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Sample records for alters extinction learning

  1. Inhibiting DNA methylation alters olfactory extinction but not acquisition learning in Apis cerana and Apis mellifera.

    Science.gov (United States)

    Gong, Zhiwen; Wang, Chao; Nieh, James C; Tan, Ken

    2016-07-01

    DNA methylation plays a key role in invertebrate acquisition and extinction memory. Honey bees have excellent olfactory learning, but the role of DNA methylation in memory formation has, to date, only been studied in Apis mellifera. We inhibited DNA methylation by inhibiting DNA methyltransferase (DNMT) with zebularine (zeb) and studied the resulting effects upon olfactory acquisition and extinction memory in two honey bee species, Apis cerana and A. mellifera. We used the proboscis extension reflex (PER) assay to measure memory. We provide the first demonstration that DNA methylation is also important in the olfactory extinction learning of A. cerana. DNMT did not reduce acquisition learning in either species. However, zeb bidirectionally and differentially altered extinction learning in both species. In particular, zeb provided 1h before acquisition learning improved extinction memory retention in A. mellifera, but reduced extinction memory retention in A. cerana. The reasons for these differences are unclear, but provide a basis for future studies to explore species-specific differences in the effects of methylation on memory formation.

  2. Inhibiting DNA methylation alters olfactory extinction but not acquisition learning in Apis cerana and Apis mellifera.

    Science.gov (United States)

    Gong, Zhiwen; Wang, Chao; Nieh, James C; Tan, Ken

    2016-07-01

    DNA methylation plays a key role in invertebrate acquisition and extinction memory. Honey bees have excellent olfactory learning, but the role of DNA methylation in memory formation has, to date, only been studied in Apis mellifera. We inhibited DNA methylation by inhibiting DNA methyltransferase (DNMT) with zebularine (zeb) and studied the resulting effects upon olfactory acquisition and extinction memory in two honey bee species, Apis cerana and A. mellifera. We used the proboscis extension reflex (PER) assay to measure memory. We provide the first demonstration that DNA methylation is also important in the olfactory extinction learning of A. cerana. DNMT did not reduce acquisition learning in either species. However, zeb bidirectionally and differentially altered extinction learning in both species. In particular, zeb provided 1h before acquisition learning improved extinction memory retention in A. mellifera, but reduced extinction memory retention in A. cerana. The reasons for these differences are unclear, but provide a basis for future studies to explore species-specific differences in the effects of methylation on memory formation. PMID:27262427

  3. Altered consolidation of extinction-like inhibitory learning in genotype-specific dysfunctional coping fostered by chronic stress in mice.

    Science.gov (United States)

    Campus, P; Maiolati, M; Orsini, C; Cabib, S

    2016-12-15

    Genetic and stress-related factors interact to foster mental disorders, possibly through dysfunctional learning. In a previous study we reported that a temporary experience of reduced food availability increases forced swim (FS)-induced helplessness tested 14days after a first experience in mice of the standard inbred C57BL/6(B6) strain but reduces it in mice of the genetically unrelated DBA/2J (D2) strain. Because persistence of FS-induced helplessness influences adaptive coping with stress challenge and involve learning processes the present study tested whether the behavioral effects of restricted feeding involved altered consolidation of FS-related learning. First, we demonstrated that restricted feeding does not influence behavior expressed on the first FS experience, supporting a specific effect on persistence rather then development of helplessness. Second, we found that FS-induced c-fos expression in the infralimbic cortex (IL) was selectively enhanced in food-restricted (FR) B6 mice and reduced in FR D2 mice, supporting opposite alterations of consolidation processes involving this brain area. Third, we demonstrated that immediate post-FS inactivation of IL prevents 24h retention of acquired helplessness by continuously free-fed mice of both strains, indicating the requirement of a functioning IL for consolidation of FS-related learning in either mouse strain. Finally, in line with the known role of IL in consolidation of extinction memories, we found that restricted feeding selectively facilitated 24h retention of an acquired extinction in B6 mice whereas impairing it in D2 mice. These findings support the conclusion that an experience of reduced food availability strain-specifically affects persistence of newly acquired passive coping strategies by altering consolidation of extinction-like inhibitory learning. PMID:27506654

  4. Context, Learning, and Extinction

    Science.gov (United States)

    Gershman, Samuel J.; Blei, David M.; Niv, Yael

    2010-01-01

    A. Redish et al. (2007) proposed a reinforcement learning model of context-dependent learning and extinction in conditioning experiments, using the idea of "state classification" to categorize new observations into states. In the current article, the authors propose an interpretation of this idea in terms of normative statistical inference. They…

  5. Behavioral tagging of extinction learning.

    Science.gov (United States)

    de Carvalho Myskiw, Jociane; Benetti, Fernando; Izquierdo, Iván

    2013-01-15

    Extinction of contextual fear in rats is enhanced by exposure to a novel environment at 1-2 h before or 1 h after extinction training. This effect is antagonized by administration of protein synthesis inhibitors anisomycin and rapamycin into the hippocampus, but not into the amygdala, immediately after either novelty or extinction training, as well as by the gene expression blocker 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole administered after novelty training, but not after extinction training. Thus, this effect can be attributed to a mechanism similar to synaptic tagging, through which long-term potentiation can be enhanced by other long-term potentiations or by exposure to a novel environment in a protein synthesis-dependent fashion. Extinction learning produces a tag at the appropriate synapses, whereas novelty learning causes the synthesis of plasticity-related proteins that are captured by the tag, strengthening the synapses that generated this tag. PMID:23277583

  6. Fibroblast Growth Factor-2 Alters the Nature of Extinction

    Science.gov (United States)

    Graham, Bronwyn M.; Richardson, Rick

    2011-01-01

    These experiments examined the effects of the NMDA-receptor (NMDAr) antagonist MK801 on reacquisition and re-extinction of a conditioned fear that had been previously extinguished before injection of fibroblast growth factor-2 (FGF2) or vehicle. Recent findings have shown that relearning and re-extinction, unlike initial learning and extinction,…

  7. Neural signals of vicarious extinction learning.

    Science.gov (United States)

    Golkar, Armita; Haaker, Jan; Selbing, Ida; Olsson, Andreas

    2016-10-01

    Social transmission of both threat and safety is ubiquitous, but little is known about the neural circuitry underlying vicarious safety learning. This is surprising given that these processes are critical to flexibly adapt to a changeable environment. To address how the expression of previously learned fears can be modified by the transmission of social information, two conditioned stimuli (CS + s) were paired with shock and the third was not. During extinction, we held constant the amount of direct, non-reinforced, exposure to the CSs (i.e. direct extinction), and critically varied whether another individual-acting as a demonstrator-experienced safety (CS + vic safety) or aversive reinforcement (CS + vic reinf). During extinction, ventromedial prefrontal cortex (vmPFC) responses to the CS + vic reinf increased but decreased to the CS + vic safety This pattern of vmPFC activity was reversed during a subsequent fear reinstatement test, suggesting a temporal shift in the involvement of the vmPFC. Moreover, only the CS + vic reinf association recovered. Our data suggest that vicarious extinction prevents the return of conditioned fear responses, and that this efficacy is reflected by diminished vmPFC involvement during extinction learning. The present findings may have important implications for understanding how social information influences the persistence of fear memories in individuals suffering from emotional disorders. PMID:27278792

  8. Extinction order and altered community structure rapidly disrupt ecosystem functioning.

    Science.gov (United States)

    Larsen, Trond H; Williams, Neal M; Kremen, Claire

    2005-05-01

    By causing extinctions and altering community structure, anthropogenic disturbances can disrupt processes that maintain ecosystem integrity. However, the relationship between community structure and ecosystem functioning in natural systems is poorly understood. Here we show that habitat loss appeared to disrupt ecosystem functioning by affecting extinction order, species richness and abundance. We studied pollination by bees in a mosaic of agricultural and natural habitats in California and dung burial by dung beetles on recently created islands in Venezuela. We found that large-bodied bee and beetle species tended to be both most extinction-prone and most functionally efficient, contributing to rapid functional loss. Simulations confirmed that extinction order led to greater disruption of function than predicted by random species loss. Total abundance declined with richness and also appeared to contribute to loss of function. We demonstrate conceptually and empirically how the non-random response of communities to disturbance can have unexpectedly large functional consequences.

  9. D-cycloserine facilitates context-specific fear extinction learning.

    Science.gov (United States)

    Bouton, Mark E; Vurbic, Drina; Woods, Amanda M

    2008-10-01

    D-cycloserine (DCS) may facilitate fear extinction learning, but the behavioral consequences and mechanisms behind this effect are not well understood at present. In this paper, we re-analyze data from previously reported null result experiments and find that rats showing above-median extinction learning during DCS treatment benefited from the drug, whereas rats showing below-median (and in this case little) extinction learning did not. Two additional experiments found that DCS facilitated extinction learning when specifically combined with a moderate, but not a small, number of extinction trials. DCS thus facilitates extinction learning only if the behavioral procedure first engages the extinction learning process. The benefits of the drug, however, were specific to the context in which extinction was learned--i.e., DCS did not prevent or influence the renewal of fear observed when the extinguished cue was tested in the original conditioning context.

  10. Impaired extinction of learned fear in rats selectively bred for high anxiety – evidence of altered neuronal processing in prefrontal-amygdala pathways

    OpenAIRE

    Muigg, Patrik; Hetzenauer, Alfred; Hauer, Gabriele; Hauschild, Markus; Gaburro, Stefano; Frank, Elisabeth; Landgraf, Rainer; Singewald, Nicolas

    2008-01-01

    The impaired extinction of acquired fear is a core symptom of anxiety disorders, such as post-traumatic stress disorder, phobias or panic disorder, and is known to be particularly resistant to existing pharmacotherapy. We provide here evidence that a similar relationship between trait anxiety and resistance to extinction of fear memory can be mimicked in a psychopathologic animal model. Wistar rat lines selectively bred for high (HAB) or low (LAB) anxiety-related behaviour were tested in a cl...

  11. Fish extinctions alter nutrient recycling in tropical freshwaters

    OpenAIRE

    McIntyre, Peter B; Jones, Laura E.; Flecker, Alexander S.; Vanni, Michael J.

    2007-01-01

    There is increasing evidence that species extinctions jeopardize the functioning of ecosystems. Overfishing and other human influences are reducing the diversity and abundance of fish worldwide, but the ecosystem-level consequences of these changes have not been assessed quantitatively. Recycling of nutrients is one important ecosystem process that is directly influenced by fish. Fish species vary widely in the rates at which they excrete nitrogen and phosphorus; thus, altering fish communiti...

  12. D-cycloserine facilitates context-specific fear extinction learning

    OpenAIRE

    Bouton, Mark E.; Vurbic, Drina; Woods, Amanda M.

    2008-01-01

    D-cycloserine (DCS) may facilitate fear extinction learning, but the behavioral consequences and mechanisms behind this effect are not well understood at present. In this article, we re-analyze data from previously-reported null-result experiments and find that rats showing above-median extinction learning during DCS treatment benefited from the drug, whereas rats showing below-median (and in this case little) extinction learning did not. Two additional experiments found that DCS facilitated ...

  13. Altered processing of contextual information during fear extinction in PTSD: an fMRI study.

    Science.gov (United States)

    Rougemont-Bücking, Ansgar; Linnman, Clas; Zeffiro, Thomas A; Zeidan, Mohamed A; Lebron-Milad, Kelimer; Rodriguez-Romaguera, Jose; Rauch, Scott L; Pitman, Roger K; Milad, Mohammed R

    2011-08-01

    Medial prefrontal cortical areas have been hypothesized to underlie altered contextual processing in posttraumatic stress disorder (PTSD). We investigated brain signaling of contextual information in this disorder. Eighteen PTSD subjects and 16 healthy trauma-exposed subjects underwent a two-day fear conditioning and extinction paradigm. On day 1, within visual context A, a conditioned stimulus (CS) was followed 60% of the time by an electric shock (conditioning). The conditioned response was then extinguished (extinction learning) in context B. On day 2, recall of the extinction memory was tested in context B. Skin conductance response (SCR) and functional magnetic resonance imaging (fMRI) data were collected during context presentations. There were no SCR group differences in any context presentation. Concerning fMRI data, during late conditioning, when context A signaled danger, PTSD subjects showed dorsal anterior cingulate cortical (dACC) hyperactivation. During early extinction, when context B had not yet fully acquired signal value for safety, PTSD subjects still showed dACC hyperactivation. During late extinction, when context B had come to signal safety, they showed ventromedial prefrontal cortex (vmPFC) hypoactivation. During early extinction recall, when context B signaled safety, they showed both vmPFC hypoactivation and dACC hyperactivation. These findings suggest that PTSD subjects show alterations in the processing of contextual information related to danger and safety. This impairment is manifest even prior to a physiologically-measured, cue-elicited fear response, and characterized by hypoactivation in vmPFC and hyperactivation in dACC. PMID:20406268

  14. Rethinking Extinction.

    Science.gov (United States)

    Dunsmoor, Joseph E; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A

    2015-10-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories. PMID:26447572

  15. Rethinking Extinction.

    Science.gov (United States)

    Dunsmoor, Joseph E; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A

    2015-10-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories.

  16. Caloric Restriction Enhances Fear Extinction Learning in Mice

    OpenAIRE

    Riddle, Megan C; McKenna, Morgan C.; Yoon, Yone J; Pattwell, Siobhan S.; Santos, Patricia Mae G; Casey, B. J.; Glatt, Charles E.

    2013-01-01

    Fear extinction learning, the ability to reassess a learned cue of danger as safe when it no longer predicts aversive events, is often dysregulated in anxiety disorders. Selective serotonin reuptake inhibitors (SSRI's) enhance neural plasticity and their ability to enhance fear extinction learning may explain their anxiolytic properties. Caloric restriction (CR) has SSRI-like effects on neural plasticity and anxiety-related behavior. We implemented CR in mice to determine its effects on condi...

  17. Glutamatergic Targets for Enhancing Extinction Learning in Drug Addiction

    OpenAIRE

    Cleva, R.M; Gass, J.T.; Widholm, J J; Olive, M.F.

    2010-01-01

    The persistence of the motivational salience of drug-related environmental cues and contexts is one of the most problematic obstacles to successful treatment of drug addiction. Behavioral approaches to extinguishing the salience of drug-associated cues, such as cue exposure therapy, have generally produced disappointing results which have been attributed to, among other things, the context specificity of extinction and inadequate consolidation of extinction learning. Extinction of any behavio...

  18. Multiple sites of extinction for a single learned response

    OpenAIRE

    Kalmbach, Brian E.; Mauk, Michael D.

    2011-01-01

    Most learned responses can be diminished by extinction, a process that can be engaged when a conditioned stimulus (CS) is presented but not reinforced. We present evidence that plasticity in at least two brain regions can mediate extinction of responses produced by trace eyelid conditioning, where the CS and the reinforcing stimulus are separated by a stimulus-free interval. We observed individual differences in the effects of blocking extinction mechanisms in the cerebellum, the structure th...

  19. Tricyclic antidepressants: effects on extinction and fear learning.

    Science.gov (United States)

    Ellison, G; Handel, J; Rogers, R; Weiss, J

    1975-01-01

    Rats trained to run an alley for a food reward were extinguished following injections of different antidepressants. When retested several days later, the animals extinguished following pretreatment with the NE reuptake blocker protriptyline showed faster running speeds than did the other groups. Other rats given electrical shocks following pretreatment with protriptyline avoided the compartment in which they had been shocked less than did animals shocked following pretreatment with other antidepressants. This implies an interferance with some aspect of the learning or consolidation process which is correlated with the degree of NE reuptake blockage. It is hypothesized that NE terminals are deactivated following frustrative nonreward or punishment by the conversion and reuptake of the released NE to an altered extinction molecule. PMID:1129357

  20. Alterations in neuronal morphology in infralimbic cortex predict resistance to fear extinction following acute stress.

    Science.gov (United States)

    Moench, Kelly M; Maroun, Mouna; Kavushansky, Alexandra; Wellman, Cara

    2016-06-01

    Dysfunction in corticolimbic circuits that mediate the extinction of learned fear responses is thought to underlie the perseveration of fear in stress-related psychopathologies, including post-traumatic stress disorder. Chronic stress produces dendritic hypertrophy in basolateral amygdala (BLA) and dendritic hypotrophy in medial prefrontal cortex, whereas acute stress leads to hypotrophy in both BLA and prelimbic cortex. Additionally, both chronic and acute stress impair extinction retrieval. Here, we examined the effects of a single elevated platform stress on extinction learning and dendritic morphology in infralimbic cortex, a region considered to be critical for extinction. Acute stress produced resistance to extinction, as well as dendritic retraction in infralimbic cortex. Spine density on apical and basilar terminal branches was unaffected by stress. However, animals that underwent conditioning and extinction had decreased spine density on apical terminal branches. Thus, whereas dendritic morphology in infralimbic cortex appears to be particularly sensitive to stress, changes in spines may more sensitively reflect learning. Further, in stressed rats that underwent conditioning and extinction, the level of extinction learning was correlated with spine densities, in that rats with poorer extinction retrieval had more immature spines and fewer thin spines than rats with better extinction retrieval, suggesting that stress may have impaired learning-related spine plasticity. These results may have implications for understanding the role of medial prefrontal cortex in learning deficits associated with stress-related pathologies. PMID:26844245

  1. Hippocampus NMDA receptors selectively mediate latent extinction of place learning.

    Science.gov (United States)

    Goodman, Jarid; Gabriele, Amanda; Packard, Mark G

    2016-09-01

    Extinction of maze learning may be achieved with or without the animal performing the previously acquired response. In typical "response extinction," animals are given the opportunity to make the previously acquired approach response toward the goal location of the maze without reinforcement. In "latent extinction," animals are not given the opportunity to make the previously acquired response and instead are confined to the previous goal location without reinforcement. Previous evidence indicates that the effectiveness of these protocols may depend on the type of memory being extinguished. Thus, one aim of the present study was to further examine the effectiveness of response and latent extinction protocols across dorsolateral striatum (DLS)-dependent response learning and hippocampus-dependent place learning tasks. In addition, previous neural inactivation experiments indicate a selective role for the hippocampus in latent extinction, but have not investigated the precise neurotransmitter mechanisms involved. Thus, the present study also examined whether latent extinction of place learning might depend on NMDA receptor activity in the hippocampus. In experiment 1, adult male Long-Evans rats were trained in a response learning task in a water plus-maze, in which animals were reinforced to make a consistent body-turn response to reach an invisible escape platform. Results indicated that response extinction, but not latent extinction, was effective at extinguishing memory in the response learning task. In experiment 2, rats were trained in a place learning task, in which animals were reinforced to approach a consistent spatial location containing the hidden escape platform. In experiment 2, animals also received intra-hippocampal infusions of the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid (AP5; 5.0 or 7.5 ug/0.5 µg) or saline vehicle immediately before response or latent extinction training. Results indicated that both extinction protocols were

  2. Hippocampus NMDA receptors selectively mediate latent extinction of place learning.

    Science.gov (United States)

    Goodman, Jarid; Gabriele, Amanda; Packard, Mark G

    2016-09-01

    Extinction of maze learning may be achieved with or without the animal performing the previously acquired response. In typical "response extinction," animals are given the opportunity to make the previously acquired approach response toward the goal location of the maze without reinforcement. In "latent extinction," animals are not given the opportunity to make the previously acquired response and instead are confined to the previous goal location without reinforcement. Previous evidence indicates that the effectiveness of these protocols may depend on the type of memory being extinguished. Thus, one aim of the present study was to further examine the effectiveness of response and latent extinction protocols across dorsolateral striatum (DLS)-dependent response learning and hippocampus-dependent place learning tasks. In addition, previous neural inactivation experiments indicate a selective role for the hippocampus in latent extinction, but have not investigated the precise neurotransmitter mechanisms involved. Thus, the present study also examined whether latent extinction of place learning might depend on NMDA receptor activity in the hippocampus. In experiment 1, adult male Long-Evans rats were trained in a response learning task in a water plus-maze, in which animals were reinforced to make a consistent body-turn response to reach an invisible escape platform. Results indicated that response extinction, but not latent extinction, was effective at extinguishing memory in the response learning task. In experiment 2, rats were trained in a place learning task, in which animals were reinforced to approach a consistent spatial location containing the hidden escape platform. In experiment 2, animals also received intra-hippocampal infusions of the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid (AP5; 5.0 or 7.5 ug/0.5 µg) or saline vehicle immediately before response or latent extinction training. Results indicated that both extinction protocols were

  3. A fundamental role for context in instrumental learning and extinction

    OpenAIRE

    Bouton, Mark E.; Todd, Travis P.

    2014-01-01

    The purpose of this article is to review recent research that has investigated the effects of context change on instrumental (operant) learning. The first part of the article discusses instrumental extinction, in which the strength of a reinforced instrumental behavior declines when reinforcers are withdrawn. The results suggest that extinction of either simple or discriminated operant behavior is relatively specific to the context in which it is learned: As in prior studies of Pavlovian exti...

  4. Behavioral and neural bases of extinction learning in Hermissenda

    Directory of Open Access Journals (Sweden)

    Joel S. Cavallo

    2014-08-01

    Full Text Available Extinction of classical conditioning is thought to produce new learning that masks or interferes with the original memory. However, research in the nudibranch Hermissenda crassicornis (H.c. has challenged this view, and instead suggested that extinction erased the original associative memory. We have re-examined extinction in H.c. to test whether extinguished associative memories can be detected on the behavioral and cellular levels, and to characterize the temporal variables involved. Associative conditioning using pairings of light (CS and rotation (US produced characteristic suppression of H.c. phototactic behavior. A single session of extinction training (repeated light-alone presentations reversed suppressed behavior back to pre-training levels when administered 15 min after associative conditioning. This effect was abolished if extinction was delayed by 23 hr, and yet was recovered using extended extinction training (three consecutive daily extinction sessions. Extinguished phototactic suppression did not spontaneously recover at any retention interval tested (2-, 24-, 48-, 72-hr, or after additional US presentations (no observed reinstatement. Extinction training (single session, 15 min interval also reversed the pairing-produced increases in light-evoked spike frequencies of Type B photoreceptors, an identified site of associative memory storage that is causally related to phototactic suppression. These results suggest that the behavioral effects of extinction training are not due to temporary suppression of associative memories, but instead represent a reversal of the underlying cellular changes necessary for the expression of learning. In the companion article, we further elucidate mechanisms responsible for extinction-produced reversal of memory-related neural plasticity in Type B photoreceptors.

  5. Altered primary production during mass-extinction events

    NARCIS (Netherlands)

    van de Schootbrugge, B.; Gollner, S.

    2013-01-01

    The Big Five mass-extinction events are characterized by dramatic changes in primary producers. Initial disturbance to primary producers is usually followed by a succession of pioneers that represent qualitative and quantitative changes in standing crops of land plants and/or phytoplankton. On land,

  6. D-cycloserine deters reacquisition of cocaine self-administration by augmenting extinction learning.

    Science.gov (United States)

    Nic Dhonnchadha, Bríd A; Szalay, Jonathan J; Achat-Mendes, Cindy; Platt, Donna M; Otto, Michael W; Spealman, Roger D; Kantak, Kathleen M

    2010-01-01

    Augmentation of cue exposure (extinction) therapy with cognitive-enhancing pharmacotherapy may offer an effective strategy to combat cocaine relapse. To investigate this possibility at the preclinical level, rats and squirrel monkeys were trained to self-administer cocaine paired with a brief visual cue. Lever pressing was subsequently extinguished by withholding cocaine injections while maintaining response-contingent presentations of the cue. The glycine partial agonist D-cycloserine (DCS; 15 and 30 mg/kg in rats, 3 and 10 mg/kg in monkeys) was evaluated for its effects on the rate of extinction and subsequent reacquisition of cocaine self-administration. Compared with vehicle, pretreatment with 30 mg/kg DCS 0.5 h before extinction training reduced the number of responses and latency to reach the extinction criterion in rats, but neither dose of DCS altered these measures in monkeys. In both species, pretreatment with the higher dose of DCS before extinction training significantly attenuated reacquisition of cocaine self-administration compared with either extinction training in the absence of DCS or DCS in the absence of explicit extinction. Furthermore, treatment with 30 mg/kg DCS accompanied by brief handling (a stress induction) immediately after but not 6 h after extinction training attenuated reacquisition of cocaine self-administration in rats. No adverse effects of 10 mg/kg DCS were evident in quantitative observational studies in monkeys. The results suggest that DCS augmented consolidation of extinction learning to deter reacquisition of cocaine self-administration in rats and monkeys. The results suggest that DCS combined with exposure therapy may constitute a rational strategy for the clinical management of cocaine relapse.

  7. Learning to inhibit the response during instrumental (operant) extinction.

    Science.gov (United States)

    Bouton, Mark E; Trask, Sydney; Carranza-Jasso, Rodrigo

    2016-07-01

    Five experiments tested implications of the idea that instrumental (operant) extinction involves learning to inhibit the learned response. All experiments used a discriminated operant procedure in which rats were reinforced for lever pressing or chain pulling in the presence of a discriminative stimulus (S), but not in its absence. In Experiment 1, extinction of the response (R) in the presence of S weakened responding in S, but equivalent nonreinforced exposure to S (without the opportunity to make R) did not. Experiment 2 replicated that result and found that extinction of R had no effect on a different R that had also been reinforced in the stimulus. In Experiments 3 and 4, rats first learned to perform several different stimulus and response combinations (S1R1, S2R1, S3R2, and S4R2). Extinction of a response in one stimulus (i.e., S1R1) transferred and weakened the same response, but not a different response, when it was tested in another stimulus (i.e., S2R1 but not S3R2). In Experiment 5, extinction still transferred between S1 and S2 when the stimuli set the occasion for R's association with different types of food pellets. The results confirm the importance of response inhibition in instrumental extinction: Nonreinforcement of the response in S causes the most effective suppression of responding, and response suppression is specific to the response but transfers and influences performance of the same response when it is occasioned by other stimuli. Theoretical and practical implications are discussed. (PsycINFO Database Record PMID:27379715

  8. Reconciling Reinforcement Learning Models with Behavioral Extinction and Renewal: Implications for Addiction, Relapse, and Problem Gambling

    Science.gov (United States)

    Redish, A. David; Jensen, Steve; Johnson, Adam; Kurth-Nelson, Zeb

    2007-01-01

    Because learned associations are quickly renewed following extinction, the extinction process must include processes other than unlearning. However, reinforcement learning models, such as the temporal difference reinforcement learning (TDRL) model, treat extinction as an unlearning of associated value and are thus unable to capture renewal. TDRL…

  9. The Effect of D-Cycloserine on Immediate vs. Delayed Extinction of Learned Fear

    Science.gov (United States)

    Langton, Julia M.; Richardson, Rick

    2010-01-01

    We compared the effect of D-cycloserine (DCS) on immediate (10 min after conditioning) and delayed (24 h after conditioning) extinction of learned fear in rats. DCS facilitated both immediate and delayed extinction when the drug was administered after extinction training. However, DCS did not facilitate immediate extinction when administered prior…

  10. Genetic disruptions of Drosophila Pavlovian learning leave extinction learning intact

    OpenAIRE

    Qin, Hongtao; Dubnau, Josh

    2009-01-01

    Individuals that experience traumatic events may develop persistent post-traumatic stress disorder (PTSD). Patients with this disorder are commonly treated with exposure therapy, which has had limited long-term success. In experimental neurobiology, fear extinction is a model for exposure therapy. In this behavioral paradigm, animals are repeatedly exposed in a safe environment to the fearful stimulus, which leads to greatly reduced fear. Studying animal models of extinction already has lead ...

  11. Mild traumatic brain injury with social defeat stress alters anxiety, contextual fear extinction, and limbic monoamines in adult rats

    Directory of Open Access Journals (Sweden)

    Daniel eDavies

    2016-04-01

    Full Text Available Mild traumatic brain injury (mTBI produces symptoms similar to those typifying posttraumatic stress disorder (PTSD in humans. We sought to determine whether a rodent model of stress concurrent with mTBI produces characteristics of PTSD such as impaired contextual fear extinction, while also examining concurrent alterations to limbic monoamine activity in brain regions relevant to fear and anxiety states. Male rats were exposed to social stress or control conditions immediately prior to mTBI induction, and 6 days later were tested either for anxiety-like behavior using the elevated plus maze (EPM, or for contextual fear conditioning and extinction. Brains were collected 24 hr after EPM testing, and tissue from various limbic regions analyzed for content of monoamines, their precursors and metabolites using HPLC with electrochemical detection. Either social defeat or mTBI alone decreased time spent in open arms of the EPM, indicating greater anxiety-like behavior. However, this effect was enhanced by the combination of treatments. Further, rats exposed to both social defeat and mTBI exhibited greater freezing within extinction sessions compared to all other groups, suggesting impaired contextual fear extinction. Social defeat combined with mTBI also had greater effects on limbic monoamines than either insult alone, particularly with respect to serotonergic effects associated with anxiety and fear learning. The results suggest social stress concurrent with mTBI produces provides a relevant animal model for studying the prevention and treatment of post-concussive psychobiological outcomes.

  12. Mild Traumatic Brain Injury with Social Defeat Stress Alters Anxiety, Contextual Fear Extinction, and Limbic Monoamines in Adult Rats.

    Science.gov (United States)

    Davies, Daniel R; Olson, Dawne; Meyer, Danielle L; Scholl, Jamie L; Watt, Michael J; Manzerra, Pasquale; Renner, Kenneth J; Forster, Gina L

    2016-01-01

    Mild traumatic brain injury (mTBI) produces symptoms similar to those typifying posttraumatic stress disorder (PTSD) in humans. We sought to determine whether a rodent model of stress concurrent with mTBI produces characteristics of PTSD such as impaired contextual fear extinction, while also examining concurrent alterations to limbic monoamine activity in brain regions relevant to fear and anxiety states. Male rats were exposed to social stress or control conditions immediately prior to mTBI induction, and 6 days later were tested either for anxiety-like behavior using the elevated plus maze (EPM), or for contextual fear conditioning and extinction. Brains were collected 24 h after EPM testing, and tissue from various limbic regions analyzed for content of monoamines, their precursors and metabolites using HPLC with electrochemical detection. Either social defeat or mTBI alone decreased time spent in open arms of the EPM, indicating greater anxiety-like behavior. However, this effect was enhanced by the combination of treatments. Further, rats exposed to both social defeat and mTBI exhibited greater freezing within extinction sessions compared to all other groups, suggesting impaired contextual fear extinction. Social defeat combined with mTBI also had greater effects on limbic monoamines than either insult alone, particularly with respect to serotonergic effects associated with anxiety and fear learning. The results suggest social stress concurrent with mTBI produces provides a relevant animal model for studying the prevention and treatment of post-concussive psychobiological outcomes. PMID:27147992

  13. Forming Competing Fear Learning and Extinction Memories in Adolescence Makes Fear Difficult to Inhibit

    Science.gov (United States)

    Baker, Kathryn D.; Richardson, Rick

    2015-01-01

    Fear inhibition is markedly impaired in adolescent rodents and humans. The present experiments investigated whether this impairment is critically determined by the animal's age at the time of fear learning or their age at fear extinction. Male rats (n = 170) were tested for extinction retention after conditioning and extinction at different ages.…

  14. No evidence for blocking the return of fear by disrupting reconsolidation prior to extinction learning.

    Science.gov (United States)

    Klucken, Tim; Kruse, Onno; Schweckendiek, Jan; Kuepper, Yvonne; Mueller, Erik M; Hennig, Juergen; Stark, Rudolf

    2016-06-01

    Fear extinction is a central model for the treatment of anxiety disorders. Initial research has reported that the single presentation of a conditioned stimulus prior to extinction learning can permanently block the return of fear. However, only few studies have explored this issue and could not always replicate the findings. The present study examined human fear extinction using a four-day design. On the first day, two neutral stimuli were paired with electrical stimulation (UCS), while a third stimulus (CS-) was not. Twenty-four hours later, one conditioned stimulus (CS+rem) and the CS- were reminded once, 10 min before extinction learning, while the other conditioned stimulus (CS+non-rem) was not presented prior to extinction learning. All stimuli were presented during extinction learning and during two re-extinction sessions (24 h and 6-months after extinction learning) without reinforcement. Blood oxygen level-dependent (BOLD) responses and skin conductance responses (SCRs) to both CS+ and the CS- were explored during acquisition, extinction, and in both re-extinction sessions. Regarding SCRs, the results showed that a single presentation of a conditioned stimulus did not block the return of fear during re-extinction: Fear recovery during re-extinction (24 h and 6-months after extinction learning) was observed for both CS+ compared with the CS- with no difference between CS+rem and CS+non-rem. Regarding BOLD-responses, no significant differences between CS+rem and CS+non-rem were found in region of interest (ROI)-analyses (amygdala, ventromedial prefrontal cortex) during extinction learning and both re-extinction sessions. Whole-brain analyses showed increased BOLD-responses to the CS+non-rem as compared to the CS+rem in several regions (e.g., middle frontal gyrus) during extinction learning and re-extinction (24 h after extinction learning). The present findings suggest that the effect of preventing the return of fear by disrupting reconsolidation seems to

  15. Dissociable Roles of Medial Orbitofrontal Cortex in Human Operant Extinction Learning

    OpenAIRE

    Finger, Elizabeth C.; Mitchell, Derek GV; Jones, Matthew; Blair, R. J. R.

    2008-01-01

    Operant extinction, which features modification of instrumental responses to stimuli following a change in associated reinforcement, is an important form of learning for organisms in dynamic environments. Animal studies have highlighted orbital and medial prefrontal cortex and amygdala as mediators of operant extinction. Yet little is known about the neural mediators of operant extinction learning in humans. Using a novel fMRI paradigm, we report dissociable functional responses in distinct r...

  16. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans.

    Science.gov (United States)

    Rabinak, Christine A; Angstadt, Mike; Lyons, Maryssa; Mori, Shoko; Milad, Mohammed R; Liberzon, Israel; Phan, K Luan

    2014-09-01

    Pre-extinction administration of Δ9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely occurs via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a functional magnetic resonance imaging (fMRI) study using a randomized, double-blind, placebo-controlled, between-subjects design (N=14/group) coupled with a standard Pavlovian fear extinction paradigm and an acute pharmacological challenge with oral dronabinol (synthetic THC) in healthy adult volunteers. We examined the effects of THC on vmPFC and HIPP activation when tested for recall of extinction learning 24 h after extinction learning. Compared to subjects who received placebo, participants who received THC showed increased vmPFC and HIPP activation to a previously extinguished conditioned stimulus (CS+E) during extinction memory recall. This study provides the first evidence that pre-extinction administration of THC modulates prefrontal-limbic circuits during fear extinction in humans and prompts future investigation to test if cannabinoid agonists can rescue or correct the impaired behavioral and neural function during extinction recall in patients with PTSD. Ultimately, the cannabinoid system may serve as a promising target for innovative intervention strategies (e.g. pharmacological enhancement of exposure-based therapy) in PTSD and other fear learning-related disorders.

  17. Extinction of conditioned fear is better learned and recalled in the morning than in the evening.

    Science.gov (United States)

    Pace-Schott, Edward F; Spencer, Rebecca M C; Vijayakumar, Shilpa; Ahmed, Nafis A K; Verga, Patrick W; Orr, Scott P; Pitman, Roger K; Milad, Mohammed R

    2013-11-01

    Sleep helps emotional memories consolidate and may promote generalization of fear extinction memory. We examined whether extinction learning and memory might differ in the morning and evening due, potentially, to circadian and/or sleep-homeostatic factors. Healthy men (N = 109) in 6 groups completed a 2-session protocol. In Session 1, fear conditioning was followed by extinction learning. Partial reinforcement with mild electric shock produced conditioned skin conductance responses (SCRs) to 2 differently colored lamps (CS+), but not a third color (CS-), within the computer image of a room (conditioning context). One CS+ (CS + E) but not the other (CS + U) was immediately extinguished by un-reinforced presentations in a different room (extinction context). Delay durations of 3 h (within AM or PM), 12 h (morning-to-evening or evening-to-morning) or 24 h (morning-to-morning or evening-to-evening) followed. In Session 2, extinction recall and contextual fear renewal were tested. We observed no significant effects of the delay interval on extinction memory but did observe an effect of time-of-day. Fear extinction was significantly better if learned in the morning (p = .002). Collapsing across CS + type, there was smaller morning differential SCR at both extinction recall (p = .003) and fear renewal (p = .005). Morning extinction recall showed better generalization from the CS + E to CS + U with the response to the CS + U significantly larger than to the CS + E only in the evening (p = .028). Thus, extinction is learned faster and its memory is better generalized in the morning. Cortisol and testosterone showed the expected greater salivary levels in the morning when higher testosterone/cortisol ratio also predicted better extinction learning. Circadian factors may promote morning extinction. Alternatively, evening homeostatic sleep pressure may impede extinction and favor recall of conditioned fear. PMID:23992769

  18. Transient inactivation of the pigeon hippocampus or the nidopallium caudolaterale during extinction learning impairs extinction retrieval in an appetitive conditioning paradigm.

    Science.gov (United States)

    Lengersdorf, Daniel; Stüttgen, Maik C; Uengoer, Metin; Güntürkün, Onur

    2014-05-15

    The majority of experiments exploring context-dependent extinction learning employ Pavlovian fear conditioning in rodents. Since mechanisms of appetitive and aversive learning are known to differ at the neuronal level, we sought to investigate extinction learning in an appetitive setting. Working with pigeons, we established a within-subject ABA renewal paradigm based on Rescorla (Q J Exp Psychol 61:1793) and combined it with pharmacological interventions during extinction. From the fear conditioning literature, it is known that both prefrontal cortex and the hippocampus are core structures for context-specific extinction learning. Accordingly, we transiently inactivated the nidopallium caudolaterale (NCL, a functional analogue of mammalian prefrontal cortex) and the hippocampus in separate experiments by intracranial infusion of the sodium-channel blocker tetrodotoxin immediately before extinction training. We find that TTX in both structures non-specifically suppresses conditioned responding, as revealed by a reduction of response rate to both the extinguished conditioned stimulus and a control stimulus which remained reinforced throughout the experiment. Furthermore, TTX during extinction training impaired later extinction retrieval assessed under drug-free conditions. This was true when responding to the extinguished stimulus was assessed in the context of extinction but not when tested in the context of acquisition, although both contexts were matched with respect to their history of conditioning. These results indicate that both NCL and hippocampus are involved in extinction learning under appetitive conditions or, more specifically, in the consolidation of extinction memory, and that their contribution to extinction is context-specific.

  19. Impaired fear extinction learning and cortico-amygdala circuit abnormalities in a common genetic mouse strain

    OpenAIRE

    Hefner, Kathryn; Whittle, Nigel; Juhasz, Jaynann; Norcross, Maxine; Karlsson, Rose-Marie; Saksida, Lisa M.; Bussey, Timothy J.; Singewald, Nicolas; Holmes, Andrew

    2008-01-01

    Fear extinction is a form of new learning that results in the inhibition of conditioned fear. Trait deficits in fear extinction are a risk factor for anxiety disorders. There are few examples of naturally-occurring animal models of impaired extinction. The present study compared fear extinction in a panel of inbred mouse strains. This strain survey revealed an impairment in fear extinction in 129/SvImJ (129S1). The phenotypic specificity of this deficit was evaluated by comparing 129S1 and C5...

  20. Extinction as New Learning versus Unlearning: Considerations from a Computer Simulation of the Cerebellum

    Science.gov (United States)

    Mauk, Michael D.; Ohyama, Tatsuya

    2004-01-01

    Like many forms of Pavlovian conditioning, eyelid conditioning displays robust extinction. We used a computer simulation of the cerebellum as a tool to consider the widely accepted view that extinction involves new, inhibitory learning rather than unlearning of acquisition. Previously, this simulation suggested basic mechanistic features of…

  1. Cued Reacquisition Trials during Extinction Weaken Contextual Renewal in Human Predictive Learning

    Science.gov (United States)

    Effting, Marieke; Vervliet, Bram; Beckers, Tom; Kindt, Merel

    2013-01-01

    Extinction is generally more context specific than acquisition, as illustrated by the renewal effect. While most strategies to counteract renewal focus on decreasing the context specificity of extinction, the present work aimed at increasing the context specificity of acquisition learning. Two experiments examined whether presenting cued…

  2. Cued reacquisition trials during extinction weaken contextual renewal in human predictive learning

    NARCIS (Netherlands)

    M. Effting; B. Vervliet; T. Beckers; M. Kindt

    2013-01-01

    Extinction is generally more context specific than acquisition, as illustrated by the renewal effect. While most strategies to counteract renewal focus on decreasing the context specificity of extinction, the present work aimed at increasing the context specificity of acquisition learning. Two exper

  3. Blockade of Dopamine Activity in the Nucleus Accumbens Impairs Learning Extinction of Conditioned Fear

    Science.gov (United States)

    Holtzman-Assif, Orit; Laurent, Vincent; Westbrook, R. Frederick

    2010-01-01

    Three experiments used rats to investigate the role of dopamine activity in learning to inhibit conditioned fear responses (freezing) in extinction. In Experiment 1, rats systemically injected with the D2 dopamine antagonist, haloperidol, froze more across multiple extinction sessions and on a drug-free retention test than control rats. In…

  4. Learning and memory in conditioned fear extinction: effects of D-cycloserine.

    Science.gov (United States)

    Vervliet, Bram

    2008-03-01

    This review addresses the effects of the cognitive enhancer D-cycloserine (DCS) on the memory processes that occur in conditioned fear extinction, which is the experimental model for exposure techniques to reduce clinical anxiety. All reported rat studies show an enhanced fear extinction effect when DCS is administered acutely before or shortly after extinction training. DCS also promotes the generalization of this fear extinction effect. In addition, DCS reduces some forms of relapse (reduced reinstatement, reduced spontaneous recovery), but not others (contextual renewal, rapid reacquisition). It is argued that this pattern of results is best explained by assuming that DCS promotes extinction learning to the background context, resulting in enhanced contextual inhibition. Four human studies have produced mixed results, but some methodological issues complicate the reported failures. It is concluded that DCS is a promising tool as an adjunct to extinction techniques in exposure treatment, but that more pre-clinical and clinical research is needed to fully characterize its behavioral consequences.

  5. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans.

    Science.gov (United States)

    Rabinak, Christine A; Angstadt, Mike; Lyons, Maryssa; Mori, Shoko; Milad, Mohammed R; Liberzon, Israel; Phan, K Luan

    2014-09-01

    Pre-extinction administration of Δ9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely occurs via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a functional magnetic resonance imaging (fMRI) study using a randomized, double-blind, placebo-controlled, between-subjects design (N=14/group) coupled with a standard Pavlovian fear extinction paradigm and an acute pharmacological challenge with oral dronabinol (synthetic THC) in healthy adult volunteers. We examined the effects of THC on vmPFC and HIPP activation when tested for recall of extinction learning 24 h after extinction learning. Compared to subjects who received placebo, participants who received THC showed increased vmPFC and HIPP activation to a previously extinguished conditioned stimulus (CS+E) during extinction memory recall. This study provides the first evidence that pre-extinction administration of THC modulates prefrontal-limbic circuits during fear extinction in humans and prompts future investigation to test if cannabinoid agonists can rescue or correct the impaired behavioral and neural function during extinction recall in patients with PTSD. Ultimately, the cannabinoid system may serve as a promising target for innovative intervention strategies (e.g. pharmacological enhancement of exposure-based therapy) in PTSD and other fear learning-related disorders. PMID:24055595

  6. Impaired contextual fear extinction learning is associated with aberrant regulation of CHD-type chromatin remodeling factors

    Directory of Open Access Journals (Sweden)

    Alexandra eWille

    2015-11-01

    Full Text Available Successful attenuation of fearful memories is a cognitive process requiring initiation of highly coordinated transcription programs. Chromatin-modulating mechanisms such as DNA methylation and histone modifications, including acetylation, are key regulators of these processes. However, knowledge concerning the role of ATP-dependent chromatin remodeling factors (ChRFs being required for successful fear extinction is lacking. Underscoring the potential importance of these factors that alter histone-DNA contacts within nucleosomes are recent genome-wide association studies linking several ChRFs to various human cognitive and psychiatric disorders. To better understand the role of ChRFs in the brain, and since to date little is known about ChRF expression in the brain, we performed a comprehensive survey of expression levels of 24 ATP-dependent remodelers across different brain areas, and we identified several distinct high molecular weight complexes by chromatographic methods. We next aimed to gain novel insight into the potential regulation of ChRFs in different brain regions in association with normal and impaired fear extinction learning. To this end, we established the 129S1/SvImJ (S1 laboratory mouse strain as a model for compromised contextual fear extinction learning that can be rescued by dietary zinc restriction. Using this model along with genetically related but fear extinction-competent 129S6/SvEv (S6 mice as controls, we found that impaired fear extinction in S1 was associated with enhanced ventral hippocampal expression of CHD1 and reduced expression of CHD5 that was normalized following successful rescue of impaired fear extinction. Moreover, a select reduction in CHD3 expression was observed in the ventral hippocampus following successful rescue of fear extinction in S1 mice. Taken together, these data provide novel insight into the regulation of specific ChRFs following an impaired cognitive process and its rescue, and they suggest

  7. Extinction learning is slower, weaker and less context specific after alcohol.

    Science.gov (United States)

    Bisby, James A; King, John A; Sulpizio, Valentina; Degeilh, Fanny; Valerie Curran, H; Burgess, Neil

    2015-11-01

    Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the following day to test fear recall from both viewpoints of the courtyard. Skin conductance responses were recorded as an index of conditioned fear. Successful fear acquisition under alcohol contrasted with impaired extinction learning evidenced by persistent conditioned responses (Experiment 1). Participants' impairments in extinction under alcohol correlated with impairments in remembering object-locations in the courtyard seen from one viewpoint when tested from the other viewpoint. Alcohol-induced extinction impairments were overcome by increasing the number of extinction trials (Experiment 2). However, a test of fear recall the next day showed persistent fear in the alcohol group across both viewpoints. Thus, alcohol impaired extinction rather than acquisition of fear, suggesting that extinction is more dependent than acquisition on alcohol-sensitive representations of spatial context. Overall, extinction learning under alcohol was slower, weaker and less context-specific, resulting in persistent fear at test that generalized to the extinction viewpoint. The selective effect on extinction suggests an effect of alcohol on prefrontal involvement, while the reduced context-specificity implicates the hippocampus. These findings have important implications for the use of alcohol by individuals with clinical anxiety disorders. PMID:26234587

  8. Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

    Directory of Open Access Journals (Sweden)

    Brackney Ryan J

    2012-12-01

    Full Text Available Abstract Background Deficient operant extinction has been hypothesized to be constitutive of ADHD dysfunction. In order to elucidate the behavioral mechanisms underlying this deficit, the performance of an animal model of ADHD, the spontaneously hypertensive rat (SHR, was compared against the performance of a control strain, the Wistar-Kyoto rat (WKY during extinction. Method Following extensive training of lever pressing under variable interval schedules of food reinforcement (reported previously, SHR and WKY rats were exposed to two sessions of extinction training. Extinction data was analyzed using the Dynamic Bi-Exponential Refractory Model (DBERM of operant performance. DBERM assumes that operant responses are organized in bouts separated by pauses; during extinction, bouts may decline across multiple dimensions, including frequency and length. DBERM parameters were estimated using hierarchical Bayesian modeling. Results SHR responded more than WKY during the first extinction session. DBERM parameter estimates revealed that, at the onset of extinction, SHR produced more response bouts than WKY. Over the course of extinction, response bouts progressively shortened for WKY but not for SHR. Conclusions Based on prior findings on the sensitivity of DBERM parameters to motivational and schedule manipulations, present data suggests that (1 more frequent response bouts in SHR are likely related to greater incentive motivation, and (2 the persistent length of bouts in SHR are likely related to a slower updating of the response-outcome association. Overall, these findings suggest specific motivational and learning deficits that may explain ADHD-related impairments in operant performance.

  9. Resting heart rate variability predicts safety learning and fear extinction in an interoceptive fear conditioning paradigm.

    Directory of Open Access Journals (Sweden)

    Meike Pappens

    Full Text Available This study aimed to investigate whether interindividual differences in autonomic inhibitory control predict safety learning and fear extinction in an interoceptive fear conditioning paradigm. Data from a previously reported study (N = 40 were extended (N = 17 and re-analyzed to test whether healthy participants' resting heart rate variability (HRV - a proxy of cardiac vagal tone - predicts learning performance. The conditioned stimulus (CS was a slight sensation of breathlessness induced by a flow resistor, the unconditioned stimulus (US was an aversive short-lasting suffocation experience induced by a complete occlusion of the breathing circuitry. During acquisition, the paired group received 6 paired CS-US presentations; the control group received 6 explicitly unpaired CS-US presentations. In the extinction phase, both groups were exposed to 6 CS-only presentations. Measures included startle blink EMG, skin conductance responses (SCR and US-expectancy ratings. Resting HRV significantly predicted the startle blink EMG learning curves both during acquisition and extinction. In the unpaired group, higher levels of HRV at rest predicted safety learning to the CS during acquisition. In the paired group, higher levels of HRV were associated with better extinction. Our findings suggest that the strength or integrity of prefrontal inhibitory mechanisms involved in safety- and extinction learning can be indexed by HRV at rest.

  10. Methylene blue facilitates the extinction of fear in an animal model of susceptibility to learned helplessness.

    Science.gov (United States)

    Wrubel, Kathryn M; Barrett, Douglas; Shumake, Jason; Johnson, S Elizabeth; Gonzalez-Lima, F

    2007-02-01

    The objectives were to (1) extend previous findings on fear extinction deficits in male congenitally helpless rats (a model for susceptibility to learned helplessness) to female congenitally helpless rats, and (2) attempt a therapeutic intervention with methylene blue, a metabolic enhancer that improves memory retention, to alleviate the predicted extinction deficits. In the first experiment, fear acquisition (four tone-shock pairings in operant chamber) was followed by extinction training (60 tones in open field). Congenitally helpless rats showed fear acquisition similar to controls but had dramatic extinction deficits, and did not display the gradual extinction curves observed in controls. Congenitally helpless rats demonstrated greater tone-evoked freezing as compared to controls in both the acquisition and extinction contexts one week after extinction training, and also in the extinction probe conducted one month later. In the second experiment (which began one month after the first experiment) congenitally helpless subjects were further exposed to tones for 5 days, each followed by 4 mg/kg methylene blue or saline IP, and had a fear renewal test in the acquisition context. Methylene blue administration improved retention of the extinction memory as demonstrated by significant decreases in fear renewal as compared to saline-administered congenitally helpless subjects. The impaired ability to extinguish fear to a traumatic memory in congenitally helpless rats supports the validity of this strain as an animal model for vulnerability to post-traumatic stress disorder, and this study further suggests that methylene blue may facilitate fear extinction as an adjunct to exposure therapy. PMID:17011803

  11. Delay and trace fear conditioning in a complex virtual learning environment - neural substrates of extinction

    Directory of Open Access Journals (Sweden)

    Heike eEwald

    2014-05-01

    Full Text Available Extinction is an important mechanism to inhibit initially acquired fear responses. There is growing evidence that the ventromedial prefrontal cortex (vmPFC inhibits the amygdala and therefore plays an important role in the extinction of delay fear conditioning. To our knowledge, there is no evidence on the role of the prefrontal cortex in the extinction of trace conditioning up to now. Thus, we compared brain structures involved in the extinction of human delay and trace fear conditioning in a between-subjects-design in an fMRI study. Participants were passively guided through a virtual environment during learning and extinction of conditioned fear. Two different lights served as conditioned stimuli (CS; as unconditioned stimulus (US a mildly painful electric stimulus was delivered. In the delay conditioning group (DCG the US was administered with offset of one light (CS+, whereas in the trace conditioning group (TCG the US was presented 4s after CS+ offset. Both groups showed insular and striatal activation during early extinction, but differed in their prefrontal activation. The vmPFC was mainly activated in the DCG, whereas the TCG showed activation of the dorsolateral prefrontal cortex (dlPFC during extinction. These results point to different extinction processes in delay and trace conditioning. VmPFC activation during extinction of delay conditioning might reflect the inhibition of the fear response. In contrast, dlPFC activation during extinction of trace conditioning may reflect modulation of working memory processes which are involved in bridging the trace interval and hold information in short term memory.

  12. Delay and trace fear conditioning in a complex virtual learning environment-neural substrates of extinction.

    Science.gov (United States)

    Ewald, Heike; Glotzbach-Schoon, Evelyn; Gerdes, Antje B M; Andreatta, Marta; Müller, Mathias; Mühlberger, Andreas; Pauli, Paul

    2014-01-01

    Extinction is an important mechanism to inhibit initially acquired fear responses. There is growing evidence that the ventromedial prefrontal cortex (vmPFC) inhibits the amygdala and therefore plays an important role in the extinction of delay fear conditioning. To our knowledge, there is no evidence on the role of the prefrontal cortex in the extinction of trace conditioning up to now. Thus, we compared brain structures involved in the extinction of human delay and trace fear conditioning in a between-subjects-design in an fMRI study. Participants were passively guided through a virtual environment during learning and extinction of conditioned fear. Two different lights served as conditioned stimuli (CS); as unconditioned stimulus (US) a mildly painful electric stimulus was delivered. In the delay conditioning group (DCG) the US was administered with offset of one light (CS+), whereas in the trace conditioning group (TCG) the US was presented 4 s after CS+ offset. Both groups showed insular and striatal activation during early extinction, but differed in their prefrontal activation. The vmPFC was mainly activated in the DCG, whereas the TCG showed activation of the dorsolateral prefrontal cortex (dlPFC) during extinction. These results point to different extinction processes in delay and trace conditioning. VmPFC activation during extinction of delay conditioning might reflect the inhibition of the fear response. In contrast, dlPFC activation during extinction of trace conditioning may reflect modulation of working memory processes which are involved in bridging the trace interval and hold information in short term memory. PMID:24904363

  13. Altered activity of the medial prefrontal cortex and amygdala during acquisition and extinction of an active avoidance task

    Directory of Open Access Journals (Sweden)

    Xilu eJiao

    2015-09-01

    Full Text Available Altered medial prefrontal cortex (mPFC and amygdala function is associated with anxiety-related disorders. While the mPFC-amygdala pathway has a clear role in fear conditioning, these structures are also involved in active avoidance. Given that avoidance perseveration represents a core symptom of anxiety disorders, the neural substrate of avoidance, especially its extinction, requires better understanding. The present study was designed to investigate the activity of mPFC and amygdala neurons during acquisition and extinction of lever-press avoidance in rats. In particular, neural activity was examined in the mPFC, intercalated cell clusters (ITCs, lateral (LA, basal (BA and central (CeA amygdala, at various time points during acquisition and extinction, using induction of the immediate early gene product, c-Fos. Neural activity was greater in the mPFC, LA, BA, and ITC during the extinction phase as compared to the acquisition phase. In contrast, the CeA was the only region that was more activated during acquisition than during extinction. Our results indicate that elevated activity in the mPFC, BA, LA and ITCs, and reduced CeA activity is associated with extinction of active avoidance. Moreover, inhibitory neurons are activated differently in the mPFC and BA during early and late phase of acquisition and extinction, suggesting their dynamic involvement in the development of avoidance response. Together, these data start to identify the key brain regions important in active avoidance behavior, areas that could be associated with avoidance perseveration in anxiety disorders.

  14. Involvement of dopamine D1/D5 and D2 receptors in context-dependent extinction learning and memory reinstatement

    Directory of Open Access Journals (Sweden)

    Marion Agnes Emma Andre

    2016-01-01

    Full Text Available Dopamine contributes to the regulation of higher order information processing and executive control. It is important for memory consolidation processes, and for the adaptation of learned responses based on experience. In line with this, under aversive learning conditions, application of dopamine receptor antagonists prior to extinction result in enhanced memory reinstatement. Here, we investigated the contribution of the dopaminergic system to extinction and memory reinstatement (renewal of an appetitive spatial learning task in rodents. Rats were trained for 3 days in a T-maze (context ‘A’ to associate a goal arm with a food reward, despite low reward probability (acquisition phase. On day 4, extinction learning (unrewarded occurred, that was reinforced by a context change (‘B’. On day 5, re-exposure to the (unrewarded ‘A’-context took place (renewal of context ‘A’, followed by extinction of context ‘A’. In control animals, significant extinction occurred on day 4, that was followed by an initial memory reinstatement (renewal on day 5, that was, in turn, succeeded by extinction of renewal. Intracerebral treatment with a D1/D5-receptor antagonist prior to the extinction trials, elicited a potent enhancement of extinction in context ‘B’. By contrast, a D1/D5-agonist impaired renewal in context ’A’. Extinction in the ‘A’ context on day 5 was unaffected by the D1/D5-ligands. Treatment with a D2-receptor antagonist prior to extinction had no overall effect on extinction in context ‘B or renewal in context ‘A’, although extinction of the renewal effect was impaired on day 5, compared to controls.Taken together, these data suggest that dopamine acting on the D1/D5-receptor modulates both acquisition and consolidation of context-dependent extinction. By contrast, the D2-receptor may contribute to context-independent aspects of this kind of extinction learning.

  15. Cocaine Self-Administration Alters the Relative Effectiveness of Multiple Memory Systems during Extinction

    Science.gov (United States)

    Gabriele, Amanda; Setlow, Barry; Packard, Mark G.

    2009-01-01

    Rats were trained to run a straight-alley maze for an oral cocaine or sucrose vehicle solution reward, followed by either response or latent extinction training procedures that engage neuroanatomically dissociable "habit" and "cognitive" memory systems, respectively. In the response extinction condition, rats performed a runway approach response…

  16. Neural correlates of two different types of extinction learning in the amygdala central nucleus.

    Science.gov (United States)

    Iordanova, Mihaela D; Deroche, Mickael L D; Esber, Guillem R; Schoenbaum, Geoffrey

    2016-01-01

    Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. This learning ensues when one experiences a change in environmental contingencies, that is, when an expected outcome fails to occur (simple extinction), or when a novel inflated expectation of a double outcome (overexpectation) is in conflict with the real outcome, and is a process that has been linked to amygdala function. Here, we show that in rats, the same neuronal population in the amygdala central nucleus updates reward expectancies and behaviour in both types of extinction, and neural changes in one paradigm are reflected in the other. This work may have implications for the management of addiction and anxiety disorders that require treatments based on the outcome omission, and disorders such as obesity that could use overexpectation, but not omission strategies.

  17. Neural correlates of two different types of extinction learning in the amygdala central nucleus.

    Science.gov (United States)

    Iordanova, Mihaela D; Deroche, Mickael L D; Esber, Guillem R; Schoenbaum, Geoffrey

    2016-01-01

    Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. This learning ensues when one experiences a change in environmental contingencies, that is, when an expected outcome fails to occur (simple extinction), or when a novel inflated expectation of a double outcome (overexpectation) is in conflict with the real outcome, and is a process that has been linked to amygdala function. Here, we show that in rats, the same neuronal population in the amygdala central nucleus updates reward expectancies and behaviour in both types of extinction, and neural changes in one paradigm are reflected in the other. This work may have implications for the management of addiction and anxiety disorders that require treatments based on the outcome omission, and disorders such as obesity that could use overexpectation, but not omission strategies. PMID:27531638

  18. Mild Traumatic Brain Injury with Social Defeat Stress Alters Anxiety, Contextual Fear Extinction, and Limbic Monoamines in Adult Rats

    OpenAIRE

    Davies, Daniel R.; Olson, Dawne; Meyer, Danielle L.; Scholl, Jamie L.; Watt, Michael J.; Manzerra, Pasquale; Renner, Kenneth J.; Forster, Gina L.

    2016-01-01

    Mild traumatic brain injury (mTBI) produces symptoms similar to those typifying posttraumatic stress disorder (PTSD) in humans. We sought to determine whether a rodent model of stress concurrent with mTBI produces characteristics of PTSD such as impaired contextual fear extinction, while also examining concurrent alterations to limbic monoamine activity in brain regions relevant to fear and anxiety states. Male rats were exposed to social stress or control conditions immediately prior to mTBI...

  19. Mild traumatic brain injury with social defeat stress alters anxiety, contextual fear extinction, and limbic monoamines in adult rats

    OpenAIRE

    Daniel eDavies; Dawne eOlson; Danielle eMeyer; Jamie eScholl; Michael eWatt; Pasquale eManzerra; Kenneth eRenner; Forster, Gina L.

    2016-01-01

    Mild traumatic brain injury (mTBI) produces symptoms similar to those typifying posttraumatic stress disorder (PTSD) in humans. We sought to determine whether a rodent model of stress concurrent with mTBI produces characteristics of PTSD such as impaired contextual fear extinction, while also examining concurrent alterations to limbic monoamine activity in brain regions relevant to fear and anxiety states. Male rats were exposed to social stress or control conditions immediately prior to mT...

  20. Extinction learning, which consists of the inhibition of retrieval, can be learned without retrieval.

    Science.gov (United States)

    de Carvalho Myskiw, Jociane; Furini, Cristiane Regina Guerino; Schmidt, Bianca; Ferreira, Flávia; Izquierdo, Ivan

    2015-01-13

    In the present study we test the hypothesis that extinction is not a consequence of retrieval in unreinforced conditioned stimulus (CS) presentation but the mere perception of the CS in the absence of a conditioned response. Animals with cannulae implanted in the CA1 region of hippocampus were subjected to extinction of contextual fear conditioning. Muscimol infused intra-CA1 before an extinction training session of contextual fear conditioning (CFC) blocks retrieval but not consolidation of extinction measured 24 h later. Additionally, this inhibition of retrieval does not affect early persistence of extinction when tested 7 d later or its spontaneous recovery after 2 wk. Furthermore, both anisomycin, an inhibitor of ribosomal protein synthesis, and rapamycin, an inhibitor of extraribosomal protein synthesis, given into the CA1, impair extinction of CFC regardless of whether its retrieval was blocked by muscimol. Therefore, retrieval performance in the first unreinforced session is not necessary for the installation, maintenance, or spontaneous recovery of extinction of CFC.

  1. Distinct Contributions of the Basolateral Amygdala and the Medial Prefrontal Cortex to Learning and Relearning Extinction of Context Conditioned Fear

    Science.gov (United States)

    Laurent, Vincent; Westbrook, R. Frederick

    2008-01-01

    We studied the roles of the basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC) in learning and relearning to inhibit context conditioned fear (freezing) in extinction. In Experiment 1, pre-extinction BLA infusion of the NMDA receptor (NMDAr) antagonist, ifenprodil, impaired the development and retention of inhibition but…

  2. Autophosphorylation of [alpha]CaMKII is Differentially Involved in New Learning and Unlearning Mechanisms of Memory Extinction

    Science.gov (United States)

    Kimura, Ryoichi; Silva, Alcino J.; Ohno, Masuo

    2008-01-01

    Accumulating evidence indicates the key role of [alpha]-calcium/calmodulin-dependent protein kinase II ([alpha]CaMKII) in synaptic plasticity and learning, but it remains unclear how this kinase participates in the processing of memory extinction. Here, we investigated the mechanism by which [alpha]CaMKII may mediate extinction by using…

  3. Extinction resistant changes in the human auditory association cortex following threat learning

    OpenAIRE

    Apergis-Schoute, Annemieke M; Schiller, Daniela; LeDoux, Joseph E.; Phelps, Elizabeth A.

    2014-01-01

    Research in humans has highlighted the importance of the amygdala for transient modulation of cortical areas for enhanced processing of emotional stimuli. However, non-human animal data has shown that amygdala dependent threat (fear) learning can also lead to long lasting changes in cortical sensitivity, persisting even after extinction of fear responses. The neural mechanisms of long-lasting traces of such conditioning in humans have not yet been explored. We used functional magnetic resonan...

  4. Dissociation of the Role of Infralimbic Cortex in Learning and Consolidation of Extinction of Recent and Remote Aversion Memory.

    Science.gov (United States)

    Awad, Walaa; Ferreira, Guillaume; Maroun, Mouna

    2015-10-01

    Medial prefrontal circuits have been reported to undergo a major reorganization over time and gradually take a more important role for remote emotional memories such as contextual fear memory or food aversion memory. The medial prefrontal cortex, and specifically its ventral subregion, the infralimbic cortex (IL), was also reported to be critical for recent memory extinction of contextual fear conditioning and conditioned odor aversion. However, its exact role in the extinction of remotely acquired information is still not clear. Using postretrieval blockade of protein synthesis or inactivation of the IL, we showed that the IL is similarly required for extinction consolidation of recent and remote fear memory. However, in odor aversion memory, the IL was only involved in extinction consolidation of recent, but not remote, memory. In contrast, only remote retrieval of aversion memory induced c-Fos activation in the IL and preretrieval inactivation of the IL with lidocaine impaired subsequent extinction of remote but not recent memory, indicating IL is necessary for extinction learning of remote aversion memory. In contrast to the effects in odor aversion, our data show that the involvement of the IL in the consolidation of fear extinction does not depend on the memory age. More importantly, our data indicate that the IL is implicated in the extinction of fear and nonfear-based associations and suggest dissociation in the engagement of the IL in the learning and consolidation of food aversion extinction over time. PMID:25872918

  5. EtOH self-administration on shuttle box avoidance learning and extinction in rats.

    Science.gov (United States)

    Pallarés, M A; Nadal, R A; Hernández-Torres, M; Ferré, N A

    1997-01-01

    The effects of ethanol on the acquisition and extinction of the two-way active avoidance response were examined in adult, male Wistar rats from two treatment groups, oral self-administration of alcohol solution (10% v/v ethanol and 3% w/v glucose in distilled water) and oral self-administration of control solution (3% w/v glucose in distilled water). Alcohol or control solutions were available 1 h per day during 15 days simultaneously with food, with free water for the rest of the day. Blood was drawn in the last day of this phase to evaluate blood ethanol levels (BEL). After this period, rats were tested in a two-bottle paradigm for 1 h per day and placed in a shuttle box immediately afterwards. This phase went lasted for 10 days. Subjects were trained to avoid an electric foot shock in the first 5 days (15 trials per day). Following this, half of the subjects were tested in an "easy extinction with punishment" (EEP) and the other half in a "difficult extinction with punishment" (DEP) of the avoidance response for the last 5 days. Alcohol accelerates the avoidance responding acquisition, and no significant effects of alcohol were seen in the extinction phase. Data are discussed in terms of the specificity of the effects of alcohol on learning. PMID:9305467

  6. Contextual change after fear acquisition affects conditioned responding and the time course of extinction learning – Implications for renewal research

    Directory of Open Access Journals (Sweden)

    Rachel eSjouwerman

    2015-12-01

    Full Text Available Context plays a central role in retrieving (fear memories. Accordingly, context manipulations are inherent to most return of fear (ROF paradigms (in particular renewal, involving contextual changes after fear extinction. Context changes are, however, also often embedded during earlier stages of ROF experiments such as context changes between fear acquisition and extinction (e.g. in ABC and ABA renewal. Previous studies using these paradigms have however focused exclusively on the context switch after extinction (i.e. renewal. Thus, the possibility of a general effect of a context switch on conditioned responding that may not be conditional to preceding extinction learning remains unstudied.Hence, the current study investigated the impact of a context switch between fear acquisition and extinction on immediate conditioned responding and on the time-course of extinction learning by using a multimodal approach. A group that underwent contextual change after fear conditioning (AB; n = 36 was compared with a group without a contextual change from acquisition to extinction (AA; n = 149, while measuring autonomic (skin conductance and fear potentiated startle measures and subjective fear ratings. Contextual change between fear acquisition and extinction had a pronounced effect on both immediate conditioned responding and on the time course of extinction learning in skin conductance responses and subjective fear ratings. This may have important implications for the mechanisms underlying and the interpretation of the renewal effect (i.e. contextual switch after extinction. Consequently, future studies should incorporate designs and statistical tests that disentangle general effects of contextual change from genuine ROF effects.

  7. Extinction-dependent alterations in corticostriatal mGluR2/3 and mGluR7 receptors following chronic methamphetamine self-administration in rats.

    Directory of Open Access Journals (Sweden)

    Marek Schwendt

    Full Text Available Methamphetamine (meth is a highly addictive and widely abused psychostimulant. Repeated use of meth can quickly lead to dependence, and may be accompanied by a variety of persistent psychiatric symptoms and cognitive impairments. The neuroadaptations underlying motivational and cognitive deficits produced by chronic meth intake remain poorly understood. Altered glutamate neurotransmission within the prefrontal cortex (PFC and striatum has been linked to both persistent drug-seeking and cognitive dysfunction. Therefore, the current study investigated changes in presynaptic mGluR receptors within corticostriatal circuitry after extended meth self-administration. Rats self-administered meth (or received yoked-saline in 1 hr/day sessions for 7 days (short-access followed by 14 days of 6 hrs/day (long-access. Rats displayed a progressive escalation of daily meth intake up to 6 mg/kg per day. After cessation of meth self-administration, rats underwent daily extinction or abstinence without extinction training for 14 days before being euthanized. Synaptosomes from the medial PFC, nucleus accumbens (NAc, and the dorsal striatum (dSTR were isolated and labeled with membrane-impermeable biotin in order to measure surface mGluR2/3 and mGluR7 receptors. Extended access to meth self-administration followed by abstinence decreased surface and total levels of mGluR2/3 receptors in the NAc and dSTR, while in the PFC, only a loss of surface mGluR2/3 and mGluR7 receptors was detected. Daily extinction trials reversed the downregulation of mGluR2/3 receptors in the NAc and dSTR and mGluR7 in the PFC, but downregulation of surface mGluR2/3 receptors in the PFC was present regardless of post-meth experience. Thus, extinction learning can selectively restore some populations of downregulated mGluRs after prolonged exposure to meth. The present findings could have implications for our understanding of the persistence (or recovery of meth-induced motivational and

  8. Can previous learning alter future plasticity mechanisms?

    Science.gov (United States)

    Crestani, Ana Paula; Quillfeldt, Jorge Alberto

    2016-02-01

    The dynamic processes related to mnemonic plasticity have been extensively researched in the last decades. More recently, studies have attracted attention because they show an unusual plasticity mechanism that is independent of the receptor most usually related to first-time learning--that is, memory acquisition-the NMDA receptor. An interesting feature of this type of learning is that a previous experience may cause modifications in the plasticity mechanism of a subsequent learning, suggesting that prior experience in a very similar task triggers a memory acquisition process that does not depend on NMDARs. The intracellular molecular cascades necessary to assist the learning process seem to depend on the activation of hippocampal CP-AMPARs. Moreover, most of these studies were performed on hippocampus-dependent tasks, even though other brain areas, such as the basolateral amygdala, also display NMDAR-independent learning.

  9. Positive allosteric modulation of mGluR5 accelerates extinction learning but not relearning following methamphetamine self-administration

    Directory of Open Access Journals (Sweden)

    Peter R Kufahl

    2012-11-01

    Full Text Available Recent studies have implicated glutamate neurotransmission as an important substrate for the extinction of conditioned behaviors, including responding for drug reinforcement. Positive allosteric modulation of the type-5 metabotropic glutamate receptor (mGluR5 in particular has emerged as a treatment strategy for the enhancement of extinction of drug-motivated behaviors. Here, we investigated the effects of the mGluR5 positive allosteric modulator CDPPB, a compound known for its cognitive enhancing effects in rodents, on extinction learning in rats with different histories of methamphetamine (METH training. Rats were trained to self-administer METH under two conditions: 16 daily sessions of short access (90 min/day, ShA, or 8 daily sessions of short access followed by 8 sessions of long access (6 hr/day, LgA. Control rats self-administered sucrose pellets in daily 30 min sessions. Next, rats were administered vehicle or 30 mg/kg CDPPB prior to 7 consecutive daily extinction sessions, subjected to additional extinction sessions to re-establish a post-treatment baseline, and then tested for reinstatement of behavior in the presence of METH- or sucrose-paired cues. Rats were then subjected to a second series of extinction sessions, preceded by vehicle or 30 mg/kg CDPPB, and an additional test for cue-triggered reinstatement. CDPPB treatment resulted in a more rapid extinction of responding on the active lever, especially in the early sessions of the first extinction sequence. However, treatment effects were minimal during subsequent cue reinstatement tests and nonexistent during the second series of extinction sessions. Rats with histories of ShA, LgA and sucrose training expressed similar behavioral sensitivities to CDPPB, with LgA rats demonstrating a modestly higher treatment effect. Positive allosteric modulation of mGluR5 may therefore have some beneficial effects on efforts to facilitate extinction learning and reduce methamphetamine seeking.

  10. [Treatment of posttraumatic stress disorder and extinction learning of traumatic memory].

    Science.gov (United States)

    Asukai, Nozomu

    2013-06-01

    Posttraumatic stress disorder (PTSD) is a debilitating psychological condition that develops following exposure to a traumatic event. The characteristic symptoms of PTSD are re-experience, avoidance, psychic numbing and hyper-arousal. The biological PTSD literature has been dramatically growing over the past three decades. PTSD symptoms related to re-experiencing the traumatic event may be conceptualized within a fear conditioning framework. Recent findings suggest that PTSD is associated with a failure of extinction learning of an acquired fear response. A fear-circuit model of PTSD posits that vmPFC fails to inhibit the amygdala, which has a crucial role in fear learning. Exposure therapy currently has the largest number of randomized clinical trials demonstrating its efficacy, and is recommended with substantial clinical confidence in treatment guidelines for PTSD. The efficacy of Prolonged Exposure (PE) was also shown for Japanese PTSD patients in a randomized controlled trial (Asukai et al., 2010). The emotional processing theory that accounts for the treatment mechanism of PE may be consistent with the hypothesis of a neurobiological mechanism in PTSD. D-cycloserine (DCS), an NMDA partial agonist, has been shown to facilitate extinction learning in animals and humans. Clinically, DCS has been shown to be a promising augmentation to PE, particularly for those who need longer treatment. PMID:25069244

  11. Avoidance Prone Individuals Self Reporting Behavioral Inhibition Exhibit Facilitated Acquisition and Altered Extinction of Conditioned Eyeblinks With Partial Reinforcement Schedules

    Directory of Open Access Journals (Sweden)

    Michael Todd Allen

    2014-10-01

    Full Text Available Avoidance in the face of novel situations or uncertainty is a prime feature of behavioral inhibition which has been put forth as a risk factor for the development of anxiety disorders. Recent work has found that behaviorally inhibited individuals acquire conditioned eyeblinks faster than non-inhibited individuals in omission and yoked paradigms in which the predictive relationship between the conditioned stimulus (CS and unconditional stimulus (US is less than optimal as compared to standard training with CS-US paired trials (Holloway et al., 2014. In the current study, we tested explicitly partial schedules in which half the trials were CS alone or US alone trials in addition to the standard CS-US paired trials. One hundred and forty nine college-aged undergraduates participated in the study. All participants completed the Adult Measure of Behavioral Inhibition (i.e., AMBI which was used to group participants as behaviorally inhibited and non-inhibited. Eyeblink conditioning consisted of 3 US alone trials, 60 acquisition trials, and 20 CS-alone extinction trials presented in one session. Conditioning stimuli were a 500 ms tone conditioned stimulus (CS and a 50-ms air puff unconditional stimulus (US. Behaviorally inhibited individuals receiving 50% partial reinforcement with CS alone or US alone trials produced facilitated acquisition as compared to non-inhibited individuals. A partial reinforcement extinction effect was evident with CS alone trials in behaviorally inhibited but not non-inhibited individuals. These current findings indicate that avoidance prone individuals self-reporting behavioral inhibition over-learn an association and are slow to extinguish conditioned responses when there is some level of uncertainty between paired trials and CS or US alone presentations.

  12. Australian Extinctions

    Science.gov (United States)

    Science Teacher, 2005

    2005-01-01

    Massive extinctions of animals and the arrival of the first humans in ancient Australia--which occurred 45,000 to 55,000 years ago--may be linked. Researchers at the Carnegie Institution, University of Colorado, Australian National University, and Bates College believe that massive fires set by the first humans may have altered the ecosystem of…

  13. Systemic or Intra-Amygdala Infusion of the Benzodiazepine, Midazolam, Impairs Learning, but Facilitates Re-Learning to Inhibit Fear Responses in Extinction

    Science.gov (United States)

    Hart, Genevra; Harris, Justin A.; Westbrook, R. Frederick

    2010-01-01

    A series of experiments used rats to study the effect of a systemic or intra-amygdala infusion of the benzodiazepine, midazolam, on learning and re-learning to inhibit context conditioned fear (freezing) responses. Rats were subjected to two context-conditioning episodes followed by extinction under drug or vehicle, or to two cycles of context…

  14. Learning and extinction of a passive avoidance response in mice with high levels of predisposition to catalepsy.

    Science.gov (United States)

    Dubrovina, N I; Zinov'ev, D R; Zinov'eva, D V; Kulikov, A V

    2009-06-01

    This report presents results obtained from comparative analysis of learning and the dynamics of extinction of a conditioned passive avoidance response in ASC mice, which were bred for a high level of predisposition to catalepsy, and in CBA and AKR mice. The following findings were obtained: 1) impairments to the extinction of the memory of fear represent an important symptom of depression in ASC mice; 2) extinction is delayed in CBA mice; and 3) new inhibitory learning occurs quickly in AKR mice. Prolonged retention of the fear memory in ASC mice appears to be related to increased anxiety on prolonged testing without a punishment. The deficit of inhibition of the fear reaction in ASC mice allows this strain to be regarded as a genetic model of depression.

  15. Learning and extinction of a passive avoidance response in mice with high levels of predisposition to catalepsy.

    Science.gov (United States)

    Dubrovina, N I; Zinov'ev, D R; Zinov'eva, D V; Kulikov, A V

    2009-06-01

    This report presents results obtained from comparative analysis of learning and the dynamics of extinction of a conditioned passive avoidance response in ASC mice, which were bred for a high level of predisposition to catalepsy, and in CBA and AKR mice. The following findings were obtained: 1) impairments to the extinction of the memory of fear represent an important symptom of depression in ASC mice; 2) extinction is delayed in CBA mice; and 3) new inhibitory learning occurs quickly in AKR mice. Prolonged retention of the fear memory in ASC mice appears to be related to increased anxiety on prolonged testing without a punishment. The deficit of inhibition of the fear reaction in ASC mice allows this strain to be regarded as a genetic model of depression. PMID:19430979

  16. Individual Differences in the Severely Retarded Child in Acquisition, Stimulus Generalization, and Extinction in Go-No-Go Discrimination Learning

    Science.gov (United States)

    Evans, P. L. C.; Hogg, J. H.

    1975-01-01

    This study relates excitatory and inhibitory personality variables of a heterogeneous group of severely retarded children to performance on a discrete trial, successive go-no-go intradimensional discrimination learning problem, which was followed by stimulus generalization tests on a color hue continuum and extinction trials. (GO)

  17. Extinction learning as a moderator of d-cycloserine efficacy for enhancing exposure therapy in posttraumatic stress disorder

    NARCIS (Netherlands)

    Kleine, R.A. de; Smits, J.A.J.; Hendriks, G.J.; Becker, E.S.; Rinck, M.

    2015-01-01

    Augmentation of exposure therapy with d-cycloserine (DCS) has proven efficacious across anxiety disorders, although results in PTSD have been mixed. Work in animals and anxiety-disordered patients suggest that the potentiating effects of DCS are dependent on the level of extinction learning during e

  18. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans

    OpenAIRE

    Rabinak, Christine A.; Angstadt, Mike; Lyons, Maryssa; Mori, Shoko; Milad, Mohammed R; Liberzon, Israel; Phan, K. Luan

    2013-01-01

    Pre-extinction administration of ∆9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely involves via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a fu...

  19. Positive Allosteric Modulation of mGluR5 Accelerates Extinction Learning but Not Relearning Following Methamphetamine Self-Administration.

    Science.gov (United States)

    Kufahl, Peter R; Hood, Lauren E; Nemirovsky, Natali E; Barabas, Piroska; Halstengard, Casey; Villa, Angel; Moore, Elisabeth; Watterson, Lucas R; Olive, M Foster

    2012-01-01

    Recent studies have implicated glutamate neurotransmission as an important substrate for the extinction of conditioned behaviors, including responding for drug reinforcement. Positive allosteric modulation of the type-5 metabotropic glutamate receptor (mGluR5) in particular has emerged as a treatment strategy for the enhancement of extinction of drug-motivated behaviors. Here, we investigated the effects of the mGluR5 positive allosteric modulator CDPPB, a compound known for its cognitive enhancing effects in rodents, on extinction learning in rats with different histories of methamphetamine (METH) training. Rats were trained to self-administer METH under two conditions: 16 daily sessions of short access (90 min/day, ShA), or eight daily sessions of short access followed by eight sessions of long access (6 h/day, LgA). Control rats self-administered sucrose pellets in daily 30 min sessions. Next, rats were administered vehicle or 30 mg/kg CDPPB prior to seven consecutive daily extinction sessions, subjected to additional extinction sessions to re-establish a post-treatment baseline, and then tested for reinstatement of behavior in the presence of METH- or sucrose-paired cues. Rats were then subjected to a second series of extinction sessions, preceded by vehicle or 30 mg/kg CDPPB, and an additional test for cue-triggered reinstatement. CDPPB treatment resulted in a more rapid extinction of responding on the active lever, especially in the early sessions of the first extinction sequence. However, treatment effects were minimal during subsequent cue reinstatement tests and non-existent during the second series of extinction sessions. Rats with histories of ShA, LgA, and sucrose training expressed similar behavioral sensitivities to CDPPB, with LgA rats demonstrating a modestly higher treatment effect. Positive allosteric modulation of mGluR5 may therefore have some beneficial effects on efforts to facilitate extinction learning and reduce methamphetamine

  20. Artificial neural networks can learn to estimate extinction rates from molecular phylogenies

    NARCIS (Netherlands)

    Bokma, Folmer

    2006-01-01

    Molecular phylogenies typically consist of only extant species, yet they allow inference of past rates of extinction, because. recently originated species are less likely to be extinct than ancient species. Despite the simple structure of the assumed underlying speciation-extinction process, paramet

  1. Fear conditioning in an abdominal pain model: neural responses during associative learning and extinction in healthy subjects.

    Directory of Open Access Journals (Sweden)

    Joswin Kattoor

    Full Text Available Fear conditioning is relevant for elucidating the pathophysiology of anxiety, but may also be useful in the context of chronic pain syndromes which often overlap with anxiety. Thus far, no fear conditioning studies have employed aversive visceral stimuli from the lower gastrointestinal tract. Therefore, we implemented a fear conditioning paradigm to analyze the conditioned response to rectal pain stimuli using fMRI during associative learning, extinction and reinstatement. In N = 21 healthy humans, visual conditioned stimuli (CS(+ were paired with painful rectal distensions as unconditioned stimuli (US, while different visual stimuli (CS(- were presented without US. During extinction, all CSs were presented without US, whereas during reinstatement, a single, unpaired US was presented. In region-of-interest analyses, conditioned anticipatory neural activation was assessed along with perceived CS-US contingency and CS unpleasantness. Fear conditioning resulted in significant contingency awareness and valence change, i.e., learned unpleasantness of a previously neutral stimulus. This was paralleled by anticipatory activation of the anterior cingulate cortex, the somatosensory cortex and precuneus (all during early acquisition and the amygdala (late acquisition in response to the CS(+. During extinction, anticipatory activation of the dorsolateral prefrontal cortex to the CS(- was observed. In the reinstatement phase, a tendency for parahippocampal activation was found. Fear conditioning with rectal pain stimuli is feasible and leads to learned unpleasantness of previously neutral stimuli. Within the brain, conditioned anticipatory activations are seen in core areas of the central fear network including the amygdala and the anterior cingulate cortex. During extinction, conditioned responses quickly disappear, and learning of new predictive cue properties is paralleled by prefrontal activation. A tendency for parahippocampal activation during

  2. Temporal Dynamics of Recovery from Extinction Shortly after Extinction Acquisition

    Science.gov (United States)

    Archbold, Georgina E.; Dobbek, Nick; Nader, Karim

    2013-01-01

    Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition…

  3. Heterogeneity in Threat Extinction Learning: Substantive and Methodological Considerations for Identifying Individual Difference in Response to Stress

    Directory of Open Access Journals (Sweden)

    Isaac Robert Galatzer-Levy

    2013-05-01

    Full Text Available Pavlovian threat (fear conditioning (PTC is an experimental paradigm that couples innate aversive stimuli with neutral cues to elicit learned defensive behavior in response to the neutral cue. PTC is commonly used as a translational model to study neurobiological and behavioral aspects of fear and anxiety disorders, including Posttraumatic Stress Disorder (PTSD. Though PTSD is a complex, multi-faceted construct that cannot be fully captured in animals, PTC is a conceptually valid model for studying the development and maintenance of learned threat responses. Thus it can inform the understanding of PTSD symptomatology. However, there are significant individual differences in posttraumatic stress that are not as of yet accounted for in studies of PTC. Individuals exposed to danger have been shown to follow distinct patterns: some adapt rapidly and completely (resilience, others adapt slowly (recovery, and others failure to adapt (chronic stress response. Identifying similar behavioral outcomes in PTC increases the translatability of this model. In this report, we present a flexible methodology for identifying individual differences in PTC by modeling latent subpopulations, or classes, characterized by defensive behavior during training. We provide evidence from a reanalysis of previously examined PTC learning and extinction data in rats to demonstrate the effectiveness of this methodology in identifying outcomes analogous to those observed in humans exposed to threat. By utilizing Latent Class Growth Analysis to test for heterogeneity in freezing behavior during threat conditioning and extinction learning in adult male outbred rats (n =58, three outcomes were identified: rapid extinction (57.3%, slow extinction (32.3%, and failure to extinguish (10.3%, indicating that heterogeneity analogous to that in naturalistic human studies is present in experimental animal studies, strengthening their translatability in understanding stress responses in

  4. Learning and memory in conditioned fear extinction: effects of d-cycloserine

    NARCIS (Netherlands)

    B. Vervliet

    2008-01-01

    This review addresses the effects of the cognitive enhancer D-cycloserine (DCS) on the memory processes that occur in conditioned fear extinction, which is the experimental model for exposure techniques to reduce clinical anxiety. All reported rat studies show an enhanced fear extinction effect when

  5. Hippocampal Context Processing during Acquisition of a Predictive Learning Task Is Associated with Renewal in Extinction Recall.

    Science.gov (United States)

    Lissek, Silke; Glaubitz, Benjamin; Schmidt-Wilcke, Tobias; Tegenthoff, Martin

    2016-05-01

    Renewal is defined as the recovery of an extinguished response if extinction and retrieval contexts differ. The context dependency of extinction, as demonstrated by renewal, has important implications for extinction-based therapies. Persons showing renewal (REN) exhibit higher hippocampal activation during extinction in associative learning than those without renewal (NOREN), demonstrating hippocampal context processing, and recruit ventromedial pFC in retrieval. Apart from these findings, brain processes generating renewal remain largely unknown. Conceivably, processing differences in task-relevant brain regions that ultimately lead to renewal may occur already in initial acquisition of associations. Therefore, in two fMRI studies, we investigated overall brain activation and hippocampal activation in REN and NOREN during acquisition of an associative learning task in response to presentation of a context alone or combined with a cue. Results of two studies demonstrated significant activation differences between the groups: In Study 1, a support vector machine classifier correctly assigned participants' brain activation patterns to REN and NOREN groups, respectively. In Study 2, REN and NOREN showed similar hippocampal involvement during context-only presentation, suggesting processing of novelty, whereas overall hippocampal activation to the context-cue compound, suggesting compound encoding, was higher in REN. Positive correlations between hippocampal activation and renewal level indicated more prominent hippocampal processing in REN. Results suggest that hippocampal processing of the context-cue compound rather than of context only during initial learning is related to a subsequent renewal effect. Presumably, REN participants use distinct encoding strategies during acquisition of context-related tasks, which reflect in their brain activation patterns and contribute to a renewal effect. PMID:26807840

  6. Chlordiazepoxide-induced released responding in extinction and punishment-conflict procedures is not altered by neonatal forebrain norepinephrine depletion.

    Science.gov (United States)

    Bialik, R J; Pappas, B A; Pusztay, W

    1982-02-01

    The effects of chlordiazepoxide (CDZ) in extinction and punishment-conflict tasks were examined in rats after neonatal systemic administration of 6-hydroxydopamine (6-OHDA) to deplete forebrain norepinephrine (NE). At about 70 days of age the rats were water deprived and trained for three days to drink in a novel apparatus. On the fourth day (test day) drinking was either extinguished by elimination of water from the drinking tube or punished by lick-contingent shock. Just prior to this test session half of the vehicle and half of the 6-OHDA treated rats were given an injection of CDZ (8 mg/kg IP). Both the injection of CDZ and forebrain NE depletion prolonged responding during extinction and reduced the suppressant effects of punishment in male rats, and these effects were of similar magnitude. Furthermore, CDZ was as effective in neonatal 6-OHDA treated male rats as in vehicle treated rats indicating that decreased transmission is ascending NE fibers caused by CDZ is not solely responsible for its behavioral effects in extinction and conflict tasks. Rather, these effects may involve cooperative mediation by both noradrenergic and serotonergic forebrain terminals. Unexpectedly, CDZ's anti-extinction effect was absent in female rats and its anti-conflict effect observed only in NE depleted females. PMID:7071081

  7. Adolescents exhibit behavioral differences from adults during instrumental learning and extinction

    OpenAIRE

    Sturman, David A.; Mandell, Daniel R.; Moghaddam, Bita

    2010-01-01

    Adolescence is associated with the development of brain regions linked to cognition and emotion. Such changes are thought to contribute to the behavioral and neuropsychiatric vulnerabilities of this period. We compared adolescent (P28-42) and adult (P60+) rats as they performed a simple instrumental task and extinction. Animals were trained to poke into a hole for a food-pellet reinforcer. After six days of training, animals underwent extinction sessions in which the previously rewarded behav...

  8. Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

    OpenAIRE

    Brackney Ryan J; Cheung Timothy HC; Herbst Katrina; Hill Jade C; Sanabria Federico

    2012-01-01

    Abstract Background Deficient operant extinction has been hypothesized to be constitutive of ADHD dysfunction. In order to elucidate the behavioral mechanisms underlying this deficit, the performance of an animal model of ADHD, the spontaneously hypertensive rat (SHR), was compared against the performance of a control strain, the Wistar-Kyoto rat (WKY) during extinction. Method Following extensive training of lever pressing under variable interval schedules of food reinforcement (reported pre...

  9. Extinction learning is slower, weaker and less context specific after alcohol

    OpenAIRE

    Bisby, J. A.; King, J. A.; Sulpizio, V.; Degeilh, F.; Valerie Curran, H.; Burgess, N.

    2015-01-01

    Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4 g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the followi...

  10. Amphibian decline and extinction: what we know and what we need to learn.

    Science.gov (United States)

    Collins, James P

    2010-11-01

    For over 350 million yr, thousands of amphibian species have lived on Earth. Since the 1980s, amphibians have been disappearing at an alarming rate, in many cases quite suddenly. What is causing these declines and extinctions? In the modern era (post 1500) there are 6 leading causes of biodiversity loss in general, and all of these acting alone or together are responsible for modern amphibian declines: commercial use; introduced/exotic species that compete with, prey on, and parasitize native frogs and salamanders; land use change; contaminants; climate change; and infectious disease. The first 3 causes are historical in the sense that they have been operating for hundreds of years, although the rate of change due to each accelerated greatly after about the mid-20th century. Contaminants, climate change, and emerging infectious diseases are modern causes suspected of being responsible for the so-called 'enigmatic decline' of amphibians in protected areas. Introduced/exotic pathogens, land use change, and infectious disease are the 3 causes with a clear role in amphibian decline as well as extinction; thus far, the other 3 causes are only implicated in decline and not extinction. The present work is a review of the 6 causes with a focus on pathogens and suggested areas where new research is needed. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that is an emerging infectious disease causing amphibian population decline and species extinction. Historically, pathogens have not been seen as a major cause of extinction, but Bd is an exception, which is why it is such an interesting, important pathogen to understand. The late 20th and early 21st century global biodiversity loss is characterized as a sixth extinction event. Amphibians are a striking example of these losses as they disappear at a rate that greatly exceeds historical levels. Consequently, modern amphibian decline and extinction is a lens through which we can view the larger story of biodiversity

  11. Amphibian decline and extinction: what we know and what we need to learn.

    Science.gov (United States)

    Collins, James P

    2010-11-01

    For over 350 million yr, thousands of amphibian species have lived on Earth. Since the 1980s, amphibians have been disappearing at an alarming rate, in many cases quite suddenly. What is causing these declines and extinctions? In the modern era (post 1500) there are 6 leading causes of biodiversity loss in general, and all of these acting alone or together are responsible for modern amphibian declines: commercial use; introduced/exotic species that compete with, prey on, and parasitize native frogs and salamanders; land use change; contaminants; climate change; and infectious disease. The first 3 causes are historical in the sense that they have been operating for hundreds of years, although the rate of change due to each accelerated greatly after about the mid-20th century. Contaminants, climate change, and emerging infectious diseases are modern causes suspected of being responsible for the so-called 'enigmatic decline' of amphibians in protected areas. Introduced/exotic pathogens, land use change, and infectious disease are the 3 causes with a clear role in amphibian decline as well as extinction; thus far, the other 3 causes are only implicated in decline and not extinction. The present work is a review of the 6 causes with a focus on pathogens and suggested areas where new research is needed. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that is an emerging infectious disease causing amphibian population decline and species extinction. Historically, pathogens have not been seen as a major cause of extinction, but Bd is an exception, which is why it is such an interesting, important pathogen to understand. The late 20th and early 21st century global biodiversity loss is characterized as a sixth extinction event. Amphibians are a striking example of these losses as they disappear at a rate that greatly exceeds historical levels. Consequently, modern amphibian decline and extinction is a lens through which we can view the larger story of biodiversity

  12. Enhanced Extinction of Cocaine Seeking in Brain-derived Neurotrophic Factor Val66Met Knock-In Mice

    Science.gov (United States)

    Briand, Lisa A.; Lee, Francis S.; Blendy, Julie A.; Pierce, R. Christopher

    2013-01-01

    The Val66Met polymorphism in the brain-derived neurotropic factor (BDNF) gene results in alterations in fear extinction behavior in both human populations and mouse models. However, it is not clear whether this polymorphism plays a similar role in extinction of appetitive behaviors. Therefore, we examined operant learning and extinction of both food and cocaine self-administration behavior in an inbred genetic knock-in mouse strain expressing the variant Bdnf. These mice provide a unique opportunity to relate alterations in aversive and appetitive extinction learning as well as provide insight into how human genetic variation can lead to differences in behavior. BDNFMet/Met mice exhibited a severe deficit in operant learning as evidenced by an inability to learn the food self-administration task. Therefore, extinction experiments were performed comparing wildtype (BDNFVal/Val) animals to mice heterozygous for the Met allele (BDNFVal/Met), which did not differ in food or cocaine self-administration behavior. In contrast to the deficit in fear extinction previously demonstrated in these mice, we found that BDNFVal/Met mice exhibited more rapid extinction of cocaine responding compared to wildtype mice. No differences were found between the genotypes in the extinction of food self-administration behavior or the reinstatement of cocaine seeking, indicating the effect is specific to extinction of cocaine responding. These results suggest that the molecular mechanisms underlying aversive and appetitive extinction are distinct from one another and BDNF may play opposing roles in the two phenomena. PMID:22394056

  13. Activation of the Infralimbic Cortex in a Fear Context Enhances Extinction Learning

    Science.gov (United States)

    Thompson, Brittany M.; Baratta, Michael V.; Biedenkapp, Joseph C.; Rudy, Jerry W.; Watkins, Linda R.; Maier, Steven F.

    2010-01-01

    Activation of the infralimbic region (IL) of the medial prefrontal cortex (mPFC) reduces conditioned fear in a variety of situations, and the IL is thought to play an important role in the extinction of conditioned fear. Here we report a series of experiments using contextual fear conditioning in which the IL is activated with the GABAa antagonist…

  14. Extinction, Spontaneous Recovery and Renewal of Flavor Preferences Based on Taste-Taste Learning

    Science.gov (United States)

    Diaz, Estrella; De la Casa, L. G.

    2011-01-01

    This paper presents evidence of extinction, spontaneous recovery and renewal in a conditioned preferences paradigm based on taste-taste associations. More specifically, in three experiments rats exposed to a simultaneous compound of citric acid-saccharin solution showed a preference for the citric solution when the preference was measured with a…

  15. Extinction in human fear conditioning

    OpenAIRE

    Hermans, Dirk; Craske, Michelle G.; Mineka, Susan; Lovibond, Peter F.

    2006-01-01

    Although most extinction research is conducted in animal laboratories, the study of extinction learning in human fear conditioning has gained increasing attention over the last decade. The most important findings from human fear extinction are reviewed in this article. Specifically, we review experimental investigations of the impact of conditioned inhibitors, conditioned exciters, context renewal, and reinstatement on fear extinction in human samples. We discuss data from laboratory studies ...

  16. Nociceptin receptor activation does not alter acquisition, expression, extinction and reinstatement of conditioned cocaine preference in mice.

    Science.gov (United States)

    Sartor, G C; Powell, S K; Wiedner, H J; Wahlestedt, C; Brothers, S P

    2016-02-01

    Growing evidence indicates that targeting nociceptin receptor (NOP) signaling may have therapeutic efficacy in treating alcohol and opioid addiction. However, little is known about the therapeutic value of selective NOP agonists for the treatment of cocaine dependence. Recently, we identified a highly selective, brain-penetrant NOP small molecule agonist (SR-8993), and using this compound, we previously showed that nociceptin receptor activation attenuated consolidation of fear-related memories. Here, we sought to determine whether SR-8993 also affects the rewarding properties of cocaine. Using a conditioned place preference (CPP) procedure, we show that SR-8993 (3 or 10 mg/kg) failed to disrupt acquisition or expression of cocaine CPP (7.5 or 15 mg/kg) in C57BL/6 mice. Additionally, SR-8993 did not affect rate of extinction or reinstatement (yohimbine- and cocaine-induced) of cocaine CPP. These studies indicate that selective activation of NOP may not be sufficient in reducing behavioral responses to cocaine. PMID:26657743

  17. Learning and extinction of conditioned hearing sensation change in the beluga whale (Delphinapterus leucas).

    Science.gov (United States)

    Nachtigall, Paul E; Supin, Alexander Ya; Estaban, Jose-Antonio; Pacini, Aude F

    2016-02-01

    Ice-dwelling beluga whales are increasingly being exposed to anthropogenic loud sounds. Beluga's hearing sensitivity measured during a warning sound just preceding a loud sound was tested using pip-train stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 32 or 45 kHz preceded the loud sound with a frequency of 32 kHz and a sound pressure level of 153 dB re 1 μPa, 2 s, hearing thresholds before the loud sound increased relative to the baseline. The threshold increased up to 15 dB for the test frequency of 45 kHz and up to 13 dB for the test frequency of 32 kHz. These threshold increases were observed during two sessions of 36 trials each. Extinction tests revealed no change during three experimental sessions followed by a jump-like return to baseline thresholds. The low exposure level producing the hearing-dampening effect (156 dB re 1 µPa(2)s in each trial), and the manner of extinction, may be considered as evidence that the observed hearing threshold increases were a demonstration of conditioned dampening of hearing when the whale anticipated the quick appearance of a loud sound in the same way demonstrated in the false killer whale and bottlenose dolphin. PMID:26659822

  18. Mere Exposure Alters Category Learning of Novel Objects

    OpenAIRE

    Folstein, Jonathan R.; Gauthier, Isabel; Palmeri, Thomas J.

    2010-01-01

    We investigated how mere exposure to complex objects with correlated or uncorrelated object features affects later category learning of new objects not seen during exposure. Correlations among pre-exposed object dimensions influenced later category learning. Unlike other published studies, the collection of pre-exposed objects provided no information regarding the categories to be learned, ruling out unsupervised or incidental category learning during pre-exposure. Instead, results are interp...

  19. Mere exposure alters category learning of novel objects

    OpenAIRE

    ThomasJPalmeri

    2010-01-01

    We investigated how mere exposure to complex objects with correlated or uncorrelated object features affects later category learning of new objects not seen during exposure. Correlations among pre-exposed object dimensions influenced later category learning. Unlike other published studies, the collection of pre-exposed objects provided no information regarding the categories to be learned, ruling out unsupervised or incidental category learning during pre-exposure. Instead, results are interp...

  20. Social stress reactivity alters reward and punishment learning

    OpenAIRE

    Cavanagh, James F.; Frank, Michael J; Allen, John J.B.

    2010-01-01

    To examine how stress affects cognitive functioning, individual differences in trait vulnerability (punishment sensitivity) and state reactivity (negative affect) to social evaluative threat were examined during concurrent reinforcement learning. Lower trait-level punishment sensitivity predicted better reward learning and poorer punishment learning; the opposite pattern was found in more punishment sensitive individuals. Increasing state-level negative affect was directly related to punishme...

  1. Microstimulation of the human substantia nigra alters reinforcement learning.

    Science.gov (United States)

    Ramayya, Ashwin G; Misra, Amrit; Baltuch, Gordon H; Kahana, Michael J

    2014-05-14

    Animal studies have shown that substantia nigra (SN) dopaminergic (DA) neurons strengthen action-reward associations during reinforcement learning, but their role in human learning is not known. Here, we applied microstimulation in the SN of 11 patients undergoing deep brain stimulation surgery for the treatment of Parkinson's disease as they performed a two-alternative probability learning task in which rewards were contingent on stimuli, rather than actions. Subjects demonstrated decreased learning from reward trials that were accompanied by phasic SN microstimulation compared with reward trials without stimulation. Subjects who showed large decreases in learning also showed an increased bias toward repeating actions after stimulation trials; therefore, stimulation may have decreased learning by strengthening action-reward associations rather than stimulus-reward associations. Our findings build on previous studies implicating SN DA neurons in preferentially strengthening action-reward associations during reinforcement learning. PMID:24828643

  2. Zinc Transporter 3 Is Involved in Learned Fear and Extinction, but Not in Innate Fear

    Science.gov (United States)

    Martel, Guillaume; Hevi, Charles; Friebely, Olivia; Baybutt, Trevor; Shumyatsky, Gleb P.

    2010-01-01

    Synaptically released Zn[superscript 2+] is a potential modulator of neurotransmission and synaptic plasticity in fear-conditioning pathways. Zinc transporter 3 (ZnT3) knock-out (KO) mice are well suited to test the role of zinc in learned fear, because ZnT3 is colocalized with synaptic zinc, responsible for its transport to synaptic vesicles,…

  3. Genetic Inactivation of D-Amino Acid Oxidase Enhances Extinction and Reversal Learning in Mice

    Science.gov (United States)

    Labrie, Viviane; Duffy, Steven; Wang, Wei; Barger, Steven W.; Baker, Glen B.; Roder, John C.

    2009-01-01

    Activation of the N-methyl-d-aspartate receptor (NMDAR) glycine site has been shown to accelerate adaptive forms of learning that may benefit psychopathologies involving cognitive and perseverative disturbances. In this study, the effects of increasing the brain levels of the endogenous NMDAR glycine site agonist D-serine, through the genetic…

  4. Beta-adrenergic receptors support attention to extinction learning that occurs in the absence, but not the presence, of a context change

    Directory of Open Access Journals (Sweden)

    Marion Emma André

    2015-05-01

    Full Text Available The noradrenergic (NA-system is an important regulator of cognitive function. It contributes to extinction learning(EL, and in disorders where EL is impaired NA-dysfunction has been postulated. We explored whether NA acting on beta-adrenergic-receptors (β-AR, regulates EL that depends on context, but is not fear-associated. We assessed behaviour in an ‘AAA’ or ‘ABA’ paradigm: rats were trained for 3 days in a T-maze(context-A to learn that a reward is consistently found in the goal arm, despite low reward probability. This was followed on day 4 by EL(unrewarded, whereby in the ABA-paradigm, EL was reinforced by a context change (B, and in the AAA-paradigm, no context change occurred. On day 5, re-exposure to the A-context (unrewarded occurred. Typically, in control ‘AAA’ animals EL occurred on day 4 that progressed further on day 5. In control ‘ABA’ animals, EL also occurred on day 4, followed by renewal of the previously learned (A behavior on day 5, that was followed (in day 5 by extinction of this behavior, as the animals realised that no food reward would be given.Treatment with the β-AR-antagonist, propranolol, prior to EL on day 4, impaired EL in the AAA-paradigm. In the ‘ABA’ paradigm, antagonist treatment on day 4, had no effect on extinction that was reinforced by a context change (B. Furthermore, β-AR-antagonism prior to renewal testing (on day 5 in the ABA-paradigm, resulted in normal renewal behavior, although subsequent extinction of responses during day 5 was prevented by the antagonist. Thus, under both treatment conditions, β-AR-antagonism prevented extinction of the behavior learned in the ‘A’ context.β-AR-blockade during an overt context change did not prevent EL, whereas β-AR were required for EL in an unchanging context. These data suggest that β-AR may support EL by reinforcing attention towards relevant changes in the previously learned experience, and that this process supports extinction

  5. Effects of neonatal amygdala lesions on fear learning, conditioned inhibition, and extinction in adult macaques.

    Science.gov (United States)

    Kazama, Andy M; Heuer, Eric; Davis, Michael; Bachevalier, Jocelyne

    2012-06-01

    Fear conditioning studies have demonstrated the critical role played by the amygdala in emotion processing. Although all lesion studies until now investigated the effect of adult-onset damage on fear conditioning, the current study assessed fear-learning abilities, as measured by fear-potentiated startle, in adult monkeys that had received neonatal neurotoxic amygdala damage or sham-operations. After fear acquisition, their abilities to learn and use a safety cue to modulate their fear to the conditioned cue, and, finally, to extinguish their response to the fear conditioned cue were measured with the AX+/BX- Paradigm. Neonatal amygdala damage retarded, but did not completely abolish, the acquisition of a learned fear. After acquisition of the fear signal, four of the six animals with neonatal amygdala lesions discriminated between the fear and safety cues and were also able to use the safety signal to reduce the potentiated-startle response and to extinguish the fear response when the air-blast was absent. In conclusion, the present results support the critical contribution of the amygdala during the early phases of fear conditioning that leads to quick, robust responses to potentially threatening stimuli, a highly adaptive process across all species and likely to be present in early infancy. The neonatal amygdala lesions also indicated the presence of amygdala-independent alternate pathways that are capable to support fear learning in the absence of a functional amygdala. This parallel processing of fear responses within these alternate pathways was also sufficient to support the ability to flexibly modulate the magnitude of the fear responses.

  6. Behavioral and neurophysiological evidence that lateral paracapsular GABAergic synapses in the basolateral amygdala contribute to the acquisition and extinction of fear learning.

    Science.gov (United States)

    Skelly, M J; Chappell, A M; Ariwodola, O J; Weiner, J L

    2016-01-01

    The lateral/basolateral amygdala (BLA) is crucial to the acquisition and extinction of Pavlovian fear conditioning, and synaptic plasticity in this region is considered to be a neural correlate of learned fear. We recently reported that activation of BLA β3-adrenoreceptors (β3-ARs) selectively enhances lateral paracapsular (LPC) feed-forward GABAergic inhibition onto BLA pyramidal neurons, and that intra-BLA infusion of a β3-AR agonist reduces measures of unconditioned anxiety-like behavior. Here, we utilized a combination of behavioral and electrophysiological approaches to characterize the role of BLA LPCs in the acquisition of fear and extinction learning in adult male Long-Evans rats. We report that intra-BLA microinjection of β3-AR agonists (BRL37344 or SR58611A, 1μg/0.5μL/side) prior to training fear conditioning or extinction blocks the expression of these behaviors 24h later. Furthermore,ex vivo low-frequency stimulation of the external capsule (LFS; 1Hz, 15min), which engages LPC synapses, induces LTP of BLA fEPSPs, while application of a β3-AR agonist (SR58611A, 5μM) induces LTD of fEPSPs when combined with LFS. Interestingly, fEPSP LTP is not observed in recordings from fear conditioned animals, suggesting that fear learning may engage the same mechanisms that induce synaptic plasticity at this input. In support of this, we find that LFS produces LTD of inhibitory postsynaptic currents (iLTD) at LPC GABAergic synapses, and that this effect is also absent following fear conditioning. Taken together, these data provide preliminary evidence that modulation of LPC GABAergic synapses can influence the acquisition and extinction of fear learning and related synaptic plasticity in the BLA.

  7. Reorganization of Learning-Associated Prefrontal Synaptic Plasticity between the Recall of Recent and Remote Fear Extinction Memory

    Science.gov (United States)

    Hugues, Sandrine; Garcia, Rene

    2007-01-01

    We have previously shown that fear extinction is accompanied by an increase of synaptic efficacy in inputs from the ventral hippocampus (vHPC) and mediodorsal thalamus (MD) to the medial prefrontal cortex (mPFC) and that disrupting these changes to mPFC synaptic transmission compromises extinction processes. The aim of this study was to examine…

  8. Altered motivation masks appetitive learning potential of obese mice.

    Science.gov (United States)

    Harb, Mazen R; Almeida, Osborne F X

    2014-01-01

    Eating depends strongly on learning processes which, in turn, depend on motivation. Conditioned learning, where individuals associate environmental cues with receipt of a reward, forms an important part of hedonic mechanisms; the latter contribute to the development of human overweight and obesity by driving excessive eating in what may become a vicious cycle. Although mice are commonly used to explore the regulation of human appetite, it is not known whether their conditioned learning of food rewards varies as a function of body mass. To address this, groups of adult male mice of differing body weights were tested two appetitive conditioning paradigms (pavlovian and operant) as well as in food retrieval and hedonic preference tests in an attempt to dissect the respective roles of learning/motivation and energy state in the regulation of feeding behavior. We found that (i) the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; (ii) higher body weight associates with increased latency to collect food reward; and (iii) mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights. Interestingly, as compared to controls, overweight and obese mice consumed smaller amounts of palatable foods (isocaloric milk or sucrose, in either the presence or absence of their respective maintenance diets: standard, low fat-high carbohydrate or high fat-high carbohydrate). Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant. Thus, overeating in mice does not reflect a reward deficiency syndrome and, in contrast to humans, mice regulate their caloric intake according to metabolic status rather than to the hedonic properties of a particular food. Together, these observations demonstrate that excess weight masks the capacity for appetitive learning in the mouse

  9. Altered motivation masks appetitive learning potential of obese mice

    Directory of Open Access Journals (Sweden)

    Mazen R. Harb

    2014-10-01

    Full Text Available Eating depends strongly on learning processes which, in turn, depend on motivation. Conditioned learning, where individuals associate environmental cues with receipt of a reward, forms an important part of hedonic mechanisms; the latter contribute to the development of human overweight and obesity by driving excessive eating in what may become a vicious cycle. Although mice are commonly used to explore the regulation of human appetite, it is not known whether their conditioned learning of food rewards varies as a function of body mass. To address this, groups of adult male mice of differing body weights were tested two appetitive conditioning paradigms (pavlovian and operant as well as in food retrieval and hedonic preference tests in an attempt to dissect the respective roles of learning/motivation and energy state in the regulation of feeding behavior. We found that i the rate of pavlovian conditioning to an appetitive reward develops as an inverse function of body weight; ii higher body weight associates with increased latency to collect food reward; and iii mice with lower body weights are more motivated to work for a food reward, as compared to animals with higher body weights. Interestingly, as compared to controls, overweight and obese mice consumed smaller amounts of palatable foods (isocaloric milk or sucrose, in either the presence or absence of their respective maintenance diets: standard, low fat-high carbohydrate or high fat-high carbohydrate. Notably, however, all groups adjusted their consumption of the different food types, such that their body weight-corrected daily intake of calories remained constant. Thus, overeating in mice does not reflect a reward deficiency syndrome and, in contrast to humans, mice regulate their caloric intake according to metabolic status rather than to the hedonic properties of a particular food. Together, these observations demonstrate that excess weight masks the capacity for appetitive learning in

  10. Theories of the dorsal bundle extinction effect.

    Science.gov (United States)

    Mason, S T; Iversen, S D

    1979-07-01

    Selective destruction of the noradrenaline systems in the rat brain using the neurotoxin 6-hydroxydopamine has been found to cause resistance to extinction in a number of behavioural situations. Several theories concerning the behavioural mechanism altered by the lesion, and hence about the role of noradrenaline in normal brain functioning, are proposed and evaluated. Theories suggesting a role for noradrenaline in activity, perseveration, internal inhibition, frustrative non-reward, motivation, or secondary reinforcement, fail to explain all the available evidence and direct tests of each theory fails to support its predictions. A model which suggests that noreadrenaline is involved in attentional behaviour, specifically in filtering out or learning to ignore irrelevant environmental stimuli, is successful in explaining all available data and direct tests of the lesioned rats' attentional capacity serve to confirm many of the predictions of an attentional theory of the dorsal bundle extinction effect.

  11. The roles of the nucleus accumbens core, dorsomedial striatum, and dorsolateral striatum in learning: performance and extinction of Pavlovian fear-conditioned responses and instrumental avoidance responses.

    Science.gov (United States)

    Wendler, Etieli; Gaspar, Jessica C C; Ferreira, Tatiana L; Barbiero, Janaína K; Andreatini, Roberto; Vital, Maria A B F; Blaha, Charles D; Winn, Philip; Da Cunha, Claudio

    2014-03-01

    This study examined the effects of bilateral excitotoxic lesions of the nucleus accumbens core (NAc-co), dorsomedial striatum (DMS) or dorsolateral striatum (DLS) of rats on the learning and extinction of Pavlovian and instrumental components of conditioned avoidance responses (CARs). None of the lesions caused sensorimotor deficits that could affect locomotion. Lesions of the NAc-co, but not DMS or DLS, decreased unconditioned and conditioned freezing. The NAc-co and DLS lesioned rats learned the 2-way active avoidance task more slowly. These results suggest: (i) CARs depend on both Pavlovian and instrumental learning; (ii) learning the Pavlovian component of CARs depends on the NAc-co; learning the instrumental component of CARs depends on the DLS, NAc and DMS; (iii) although the NAc-co is also needed for learning the instrumental component, it is not clear whether it plays a role in learning the instrumental component per se or if it simply allows learning of the Pavlovian component which is a pre-condition for learning the instrumental component; (iv) we did not find evidence that the DMS and DLS play the same roles in habit and goal-directed aspects of the instrumental component of CARs as observed in appetitive motivated instrumental responding.

  12. M-Type Potassium Channels Modulate the Intrinsic Excitability of Infralimbic Neurons and Regulate Fear Expression and Extinction

    OpenAIRE

    Santini, Edwin; James T. Porter

    2010-01-01

    Growing evidence indicates that the activity of infralimbic prefrontal cortex (IL) is critical for inhibiting inappropriate fear responses following extinction learning. Recently, we showed that fear conditioning and extinction alter the intrinsic excitability and bursting of IL pyramidal neurons in brain slices. IL neurons from Sprague Dawley rats expressing high fear had lower intrinsic excitability and bursting than those from rats expressing low fear, suggesting that regulating the intrin...

  13. Learning by Living: Life-Altering Medical Education through Nursing Home-Based Experiential Learning

    Science.gov (United States)

    Gugliucci, Marilyn R.; Weiner, Audrey

    2013-01-01

    The University of New England College of Osteopathic Medicine Learning by Living Project (referred to as Learning by Living) was piloted in 2006 as an experiential medical education learning model. Since its inception, medical and other health professions students have been "admitted" into nursing homes to live the life of an older adult nursing…

  14. Effects of rapid eye movement sleep deprivation on fear extinction recall and prediction error signaling.

    Science.gov (United States)

    Spoormaker, Victor I; Schröter, Manuel S; Andrade, Kátia C; Dresler, Martin; Kiem, Sara A; Goya-Maldonado, Roberto; Wetter, Thomas C; Holsboer, Florian; Sämann, Philipp G; Czisch, Michael

    2012-10-01

    In a temporal difference learning approach of classical conditioning, a theoretical error signal shifts from outcome deliverance to the onset of the conditioned stimulus. Omission of an expected outcome results in a negative prediction error signal, which is the initial step towards successful extinction and may therefore be relevant for fear extinction recall. As studies in rodents have observed a bidirectional relationship between fear extinction and rapid eye movement (REM) sleep, we aimed to test the hypothesis that REM sleep deprivation impairs recall of fear extinction through prediction error signaling in humans. In a three-day design with polysomnographically controlled REM sleep deprivation, 18 young, healthy subjects performed a fear conditioning, extinction and recall of extinction task with visual stimuli, and mild electrical shocks during combined functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) measurements. Compared to the control group, the REM sleep deprivation group had increased SCR scores to a previously extinguished stimulus at early recall of extinction trials, which was associated with an altered fMRI time-course in the left middle temporal gyrus. Post-hoc contrasts corrected for measures of NREM sleep variability also revealed between-group differences primarily in the temporal lobe. Our results demonstrate altered prediction error signaling during recall of fear extinction after REM sleep deprivation, which may further our understanding of anxiety disorders in which disturbed sleep and impaired fear extinction learning coincide. Moreover, our findings are indicative of REM sleep related plasticity in regions that also show an increase in activity during REM sleep.

  15. Role of Dopamine 2 Receptor in Impaired Drug-Cue Extinction in Adolescent Rats.

    Science.gov (United States)

    Zbukvic, Isabel C; Ganella, Despina E; Perry, Christina J; Madsen, Heather B; Bye, Christopher R; Lawrence, Andrew J; Kim, Jee Hyun

    2016-06-01

    Adolescent drug users display resistance to treatment such as cue exposure therapy (CET), as well as increased liability to relapse. The basis of CET is extinction learning, which involves dopamine signaling in the medial prefrontal cortex (mPFC). This system undergoes dramatic alterations during adolescence. Therefore, we investigated extinction of a cocaine-associated cue in adolescent and adult rats. While cocaine self-administration and lever-alone extinction were not different between the two ages, we observed that cue extinction reduced cue-induced reinstatement in adult but not adolescent rats. Infusion of the selective dopamine 2 receptor (D2R)-like agonist quinpirole into the infralimbic cortex (IL) of the mPFC prior to cue extinction significantly reduced cue-induced reinstatement in adolescents. This effect was replicated by acute systemic treatment with the atypical antipsychotic aripiprazole (Abilify), a partial D2R-like agonist. These data suggest that adolescents may be more susceptible to relapse due to a deficit in cue extinction learning, and highlight the significance of D2R signaling in the IL for cue extinction during adolescence. These findings inspire new tactics for improving adolescent CET, with aripiprazole representing an exciting potential pharmacological adjunct for behavioral therapy. PMID:26946126

  16. Context and Behavioral Processes in Extinction

    Science.gov (United States)

    Bouton, Mark E.

    2004-01-01

    This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related…

  17. Immediate Extinction Causes a Less Durable Loss of Performance than Delayed Extinction following Either Fear or Appetitive Conditioning

    Science.gov (United States)

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In…

  18. Serotonin transporter polyadenylation polymorphism modulates the retention of fear extinction memory.

    Science.gov (United States)

    Hartley, Catherine A; McKenna, Morgan C; Salman, Rabia; Holmes, Andrew; Casey, B J; Phelps, Elizabeth A; Glatt, Charles E

    2012-04-01

    Growing evidence suggests serotonin's role in anxiety and depression is mediated by its effects on learned fear associations. Pharmacological and genetic manipulations of serotonin signaling in mice alter the retention of fear extinction learning, which is inversely associated with anxious temperament in mice and humans. Here, we test whether genetic variation in serotonin signaling in the form of a common human serotonin transporter polyadenylation polymorphism (STPP/rs3813034) is associated with spontaneous fear recovery after extinction. We show that the risk allele of this polymorphism is associated with impaired retention of fear extinction memory and heightened anxiety and depressive symptoms. These STPP associations in humans mirror the phenotypic effects of serotonin transporter knockout in mice, highlighting the STPP as a potential genetic locus underlying interindividual differences in serotonin transporter function in humans. Furthermore, we show that the serotonin transporter polyadenylation profile associated with the STPP risk allele is altered through the chronic administration of fluoxetine, a treatment that also facilitates retention of extinction learning. The propensity to form persistent fear associations due to poor extinction recall may be an intermediate phenotype mediating the effects of genetic variation in serotonergic function on anxiety and depression. The consistency and specificity of these data across species provide robust support for this hypothesis and suggest that the little-studied STPP may be an important risk factor for mood and anxiety disorders in humans.

  19. NMDA receptor blockade in the basolateral amygdala disrupts consolidation of stimulus-reward memory and extinction learning during reinstatement of cocaine-seeking in an animal model of relapse

    OpenAIRE

    Feltenstein, Matthew W.; See, Ronald E.

    2007-01-01

    Previous research from our laboratory has implicated the basolateral amygdala (BLA) complex in the acquisition and consolidation of cue-cocaine associations, as well as extinction learning, which may regulate the long-lasting control of conditioned stimuli (CS) over drug-seeking behavior. Given the well established role of NMDA glutamate receptor activation in other forms of amygdalar-based learning, we predicted that BLA-mediated drug-cue associative learning would be NMDA receptor dependent...

  20. Learning alters theta amplitude, theta-gamma coupling and neuronal synchronization in inferotemporal cortex

    Directory of Open Access Journals (Sweden)

    Nicol Alister U

    2011-06-01

    which are correlated with behavioral performance. A network model which can reproduce these changes suggests that a key function of such learning-evoked alterations in theta and theta-nested gamma activity may be increased temporal desynchronization in neuronal firing leading to optimal timing of inputs to downstream neural networks potentiating their responses. In this way learning can produce potentiation in neural networks simply through altering the temporal pattern of their inputs.

  1. Impaired extinction of fear conditioning after REM deprivation is magnified by rearing in an enriched environment.

    Science.gov (United States)

    Hunter, Amy Silvestri

    2015-07-01

    Evidence from both human and animal studies indicates that rapid eye movement sleep (REM) is essential for the acquisition and retention of information, particularly of an emotional nature. Learning and memory can also be impacted by manipulation of housing condition such as exposure to an enriched environment (EE). This study investigated the effects of REM deprivation and EE, both separately and combined, on the extinction of conditioned fear in rats. Consistent with prior studies, conditioning was enhanced in EE-reared rats and extinction was impaired in REM deprived rats. In addition, rats exposed to both REM deprivation and EE showed the greatest impairment in extinction, with effects persisting through the first two days of extinction training. This study is the first to explore the combination of REM deprivation and EE and suggests that manipulations that alter sleep, particularly REM, can have persisting deleterious effects on emotional memory processing.

  2. Genetic gating of human fear learning and extinction: possible implications for gene-environment interaction in anxiety disorder.

    Science.gov (United States)

    Lonsdorf, Tina B; Weike, Almut I; Nikamo, Pernilla; Schalling, Martin; Hamm, Alfons O; Ohman, Arne

    2009-02-01

    Pavlovian fear conditioning is a widely used model of the acquisition and extinction of fear. Neural findings suggest that the amygdala is the core structure for fear acquisition, whereas prefrontal cortical areas are given pivotal roles in fear extinction. Forty-eight volunteers participated in a fear-conditioning experiment, which used fear potentiation of the startle reflex as the primary measure to investigate the effect of two genetic polymorphisms (5-HTTLPR and COMTval158met) on conditioning and extinction of fear. The 5-HTTLPR polymorphism, located in the serotonin transporter gene, is associated with amygdala reactivity and neuroticism, whereas the COMTval158met polymorphism, which is located in the gene coding for catechol-O-methyltransferase (COMT), a dopamine-degrading enzyme, affects prefrontal executive functions. Our results show that only carriers of the 5-HTTLPR s allele exhibited conditioned startle potentiation, whereas carriers of the COMT met/met genotype failed to extinguish conditioned fear. These results may have interesting implications for understanding gene-environment interactions in the development and treatment of anxiety disorders.

  3. Learning and altering behaviours by reinforcement: Neurocognitive differences between children and adults

    Directory of Open Access Journals (Sweden)

    E. Shephard

    2014-01-01

    Full Text Available This study examined neurocognitive differences between children and adults in the ability to learn and adapt simple stimulus–response associations through feedback. Fourteen typically developing children (mean age = 10.2 and 15 healthy adults (mean age = 25.5 completed a simple task in which they learned to associate visually presented stimuli with manual responses based on performance feedback (acquisition phase, and then reversed and re-learned those associations following an unexpected change in reinforcement contingencies (reversal phase. Electrophysiological activity was recorded throughout task performance. We found no group differences in learning-related changes in performance (reaction time, accuracy or in the amplitude of event-related potentials (ERPs associated with stimulus processing (P3 ERP or feedback processing (feedback-related negativity; FRN during the acquisition phase. However, children's performance was significantly more disrupted by the reversal than adults and FRN amplitudes were significantly modulated by the reversal phase in children but not adults. These findings indicate that children have specific difficulties with reinforcement learning when acquired behaviours must be altered. This may be caused by the added demands on immature executive functioning, specifically response monitoring, created by the requirement to reverse the associations, or a developmental difference in the way in which children and adults approach reinforcement learning.

  4. Extinction in young massive clusters

    Science.gov (United States)

    De Marchi, Guido; Panagia, Nino

    2016-01-01

    Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, causing considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars (luminosities, effective temperatures, masses, ages, etc.) we must understand and measure the local extinction law. We have developed a powerful method to unambiguously determine the extinction law everywhere across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC) and are applying it to young massive clusters in the Local Group. In the Large Magellanic Cloud, with about 20 RC stars per arcmin2, for each field we can easily derive an accurate extinction curve over the entire wavelength range of the photometry. As an example, we present the extinction law of the Tarantula nebula (30 Dor) based on thousands of stars observed as part of the Hubble Tarantula Treasury Project. We discuss how the incautious adoption of the Milky Way extinction law in the analysis of massive star forming regions may lead to serious underestimates of the fluxes and of the star formation rates by factors of 2 or more.

  5. Outcome-Specific Transfer between Predictive and Instrumental Learning Is Unaffected by Extinction but Reversed by Counterconditioning in Human Participants

    Science.gov (United States)

    Rosas, Juan M.; Paredes-Olay, Maria C.; Garcia-Gutierrez, Ana; Espinosa, Juan J.; Abad, Maria J. F.

    2010-01-01

    Three experiments were conducted to explore the effects of different interference treatments upon outcome-specific transfer from predictive learning to instrumental responding. A computer game was designed in which participants had to defend Andalusia from navy and air-force attacks. Participants learned the relationship between two instrumental…

  6. Learning to produce speech with an altered vocal tract: The role of auditory feedback

    Science.gov (United States)

    Jones, Jeffery A.; Munhall, K. G.

    2003-01-01

    Modifying the vocal tract alters a speaker's previously learned acoustic-articulatory relationship. This study investigated the contribution of auditory feedback to the process of adapting to vocal-tract modifications. Subjects said the word /tas/ while wearing a dental prosthesis that extended the length of their maxillary incisor teeth. The prosthesis affected /s/ productions and the subjects were asked to learn to produce ``normal'' /s/'s. They alternately received normal auditory feedback and noise that masked their natural feedback during productions. Acoustic analysis of the speakers' /s/ productions showed that the distribution of energy across the spectra moved toward that of normal, unperturbed production with increased experience with the prosthesis. However, the acoustic analysis did not show any significant differences in learning dependent on auditory feedback. By contrast, when naive listeners were asked to rate the quality of the speakers' utterances, productions made when auditory feedback was available were evaluated to be closer to the subjects' normal productions than when feedback was masked. The perceptual analysis showed that speakers were able to use auditory information to partially compensate for the vocal-tract modification. Furthermore, utterances produced during the masked conditions also improved over a session, demonstrating that the compensatory articulations were learned and available after auditory feedback was removed.

  7. Extinction memory is impaired in schizophrenia

    Science.gov (United States)

    Holt, Daphne. J.; Lebron-Milad, Kelimer; Milad, Mohammed R.; Rauch, Scott L.; Pitman, Roger K.; Orr, Scott P.; Cassidy, Brittany S.; Walsh, Jared P.; Goff, Donald C.

    2013-01-01

    Background Schizophrenia is associated with abnormalities in emotional processing and social cognition, which may result from disruption of the underlying neural mechanism(s) governing emotional learning and memory. To investigate this possibility, we measured the acquisition and extinction of conditioned fear responses and delayed recall of extinction in schizophrenia and control subjects. Methods 28 schizophrenia and 18 demographically-matched control subjects underwent a two-day fear conditioning, extinction learning and extinction recall procedure, in which skin conductance response (SCR) magnitude was used as the index of conditioned responses. Results During fear acquisition, 83% of the controls and 57% of the patients showed autonomic responsivity (‘responders’), and the patients showed larger SCRs to the stimulus that was not paired with the unconditioned stimulus (CS−) than the controls. Within the responder group, there was no difference between the patients and controls in levels of extinction learning; however, the schizophrenia patients showed significant impairment, relative to the controls, in context-dependent recall of the extinction memory. In addition, delusion severity in the patients correlated with baseline skin conductance levels. Conclusions These data are consistent with prior evidence for a heightened neural response to innocuous stimuli in schizophrenia and elevated arousal levels in psychosis. The finding of deficient extinction recall in schizophrenia patients who showed intact extinction learning suggests that schizophrenia is associated with a disturbance in the neural processes supporting emotional memory. PMID:18986648

  8. Altered risk-based decision making following adolescent alcohol use results from an imbalance in reinforcement learning in rats.

    Directory of Open Access Journals (Sweden)

    Jeremy J Clark

    Full Text Available Alcohol use during adolescence has profound and enduring consequences on decision-making under risk. However, the fundamental psychological processes underlying these changes are unknown. Here, we show that alcohol use produces over-fast learning for better-than-expected, but not worse-than-expected, outcomes without altering subjective reward valuation. We constructed a simple reinforcement learning model to simulate altered decision making using behavioral parameters extracted from rats with a history of adolescent alcohol use. Remarkably, the learning imbalance alone was sufficient to simulate the divergence in choice behavior observed between these groups of animals. These findings identify a selective alteration in reinforcement learning following adolescent alcohol use that can account for a robust change in risk-based decision making persisting into later life.

  9. Role of the hippocampus in contextual modulation of fear extinction

    Institute of Scientific and Technical Information of China (English)

    Lingzhi Kong; Xihong Wu; Liang Li

    2008-01-01

    Fear extinction is an important form of emotional learning, and affects neural plasticity. Cue fear extinction is a classical form of inhibitory learning that can be used as an exposure-based treatment for phobia, because the long-term extinction memory produced during cue fear extinction can limit the over-expression of fear. The expression of this inhibitory memory partly depends on the context in which the extinction learning occurs. Studies such as transient inhibition, electrophysiology and brain imaging have proved that the hippocampus - an important structure in the limbic system - facilitates memory retrieval by contextual cues.Mediation of the hippocampus-medial prefrontal lobe circuit may be the neurobiological basis of this process.This article has reviewed the role of the hippocampus in the learning and retrieval of fear extinction.Contextual modulation of fear extinction may rely on a neural network consisting of the hippocampus, the medial prefrontal cortex and the amygdala.

  10. A sphingolipid mechanism for behavioral extinction.

    Science.gov (United States)

    Huston, Joseph P; Kornhuber, Johannes; Mühle, Christiane; Japtok, Lukasz; Komorowski, Mara; Mattern, Claudia; Reichel, Martin; Gulbins, Erich; Kleuser, Burkhard; Topic, Bianca; De Souza Silva, Maria A; Müller, Christian P

    2016-05-01

    Reward-dependent instrumental behavior must continuously be re-adjusted according to environmental conditions. Failure to adapt to changes in reward contingencies may incur psychiatric disorders like anxiety and depression. When an expected reward is omitted, behavior undergoes extinction. While extinction involves active re-learning, it is also accompanied by emotional behaviors indicative of frustration, anxiety, and despair (extinction-induced depression). Here, we report evidence for a sphingolipid mechanism in the extinction of behavior. Rapid extinction, indicating efficient re-learning, coincided with a decrease in the activity of the enzyme acid sphingomyelinase (ASM), which catalyzes turnover of sphingomyelin to ceramide, in the dorsal hippocampus of rats. The stronger the decline in ASM activity, the more rapid was the extinction. Sphingolipid-focused lipidomic analysis showed that this results in a decline of local ceramide species in the dorsal hippocampus. Ceramides shape the fluidity of lipid rafts in synaptic membranes and by that way can control neural plasticity. We also found that aging modifies activity of enzymes and ceramide levels in selective brain regions. Aging also changed how the chronic treatment with corticosterone (stress) or intranasal dopamine modified regional enzyme activity and ceramide levels, coinciding with rate of extinction. These data provide first evidence for a functional ASM-ceramide pathway in the brain involved in the extinction of learned behavior. This finding extends the known cellular mechanisms underlying behavioral plasticity to a new class of membrane-located molecules, the sphingolipids, and their regulatory enzymes, and may offer new treatment targets for extinction- and learning-related psychopathological conditions. Sphingolipids are common lipids in the brain which form lipid domains at pre- and postsynaptic membrane compartments. Here we show a decline in dorsal hippocampus ceramide species together with a

  11. Prenatal exposure to gamma/neutron irradiation: Sensorimotor alterations and paradoxical effects on learning

    International Nuclear Information System (INIS)

    The effects of prenatal exposure on gamma/neutron radiations (0.5 Gy at about the 18th day of fetal life) were studied in a hybrid strain of mice (DBA/Cne males x C57BL/Cne females). During ontogeny, measurements of sensorimotor reflexes revealed in prenatally irradiated mice (1) a delay in sensorial development, (2) deficits in tests involving body motor control, and (3) a reduction of both motility and locomotor activity scores. In adulthood, the behaviour of prenatally irradiated and control mice was examined in the open field test and in reactivity to novelty. Moreover, their learning performance was compared in several situations. The results show that, in the open field test, only rearings were more frequent in irradiated mice. In the presence of a novel object, significant sex x treatment interactions were observed since ambulation and leaning against the novel object increased in irradiated females but decreased in irradiated males. Finally, when submitted to different learning tasks, irradiated mice were impaired in the radial maze, but paradoxically exhibited higher avoidance scores than control mice, possibly because of their low pain thresholds. Taken together, these observations indicate that late prenatal gamma/neutron irradiation induces long lasting alterations at the sensorimotor level which, in turn, can influence learning abilities of adult mice

  12. Prenatal exposure to gamma/neutron irradiation: Sensorimotor alterations and paradoxical effects on learning

    Energy Technology Data Exchange (ETDEWEB)

    Di Cicco, D.; Antal, S.; Ammassari-Teule, M. (Istituto di Psicobiologia e Psicofarmacologia del CNR, Rome (Italy))

    1991-01-01

    The effects of prenatal exposure on gamma/neutron radiations (0.5 Gy at about the 18th day of fetal life) were studied in a hybrid strain of mice (DBA/Cne males x C57BL/Cne females). During ontogeny, measurements of sensorimotor reflexes revealed in prenatally irradiated mice (1) a delay in sensorial development, (2) deficits in tests involving body motor control, and (3) a reduction of both motility and locomotor activity scores. In adulthood, the behaviour of prenatally irradiated and control mice was examined in the open field test and in reactivity to novelty. Moreover, their learning performance was compared in several situations. The results show that, in the open field test, only rearings were more frequent in irradiated mice. In the presence of a novel object, significant sex x treatment interactions were observed since ambulation and leaning against the novel object increased in irradiated females but decreased in irradiated males. Finally, when submitted to different learning tasks, irradiated mice were impaired in the radial maze, but paradoxically exhibited higher avoidance scores than control mice, possibly because of their low pain thresholds. Taken together, these observations indicate that late prenatal gamma/neutron irradiation induces long lasting alterations at the sensorimotor level which, in turn, can influence learning abilities of adult mice.

  13. Heterogeneity in threat extinction learning: substantive and methodological considerations for identifying individual difference in response to stress

    OpenAIRE

    Isaac Robert Galatzer-Levy; Bonanno, George A.; David E Bush; Joe eLeDoux

    2013-01-01

    Pavlovian threat (fear) conditioning (PTC) is an experimental paradigm that couples innate aversive stimuli with neutral cues to elicit learned defensive behavior in response to the neutral cue. PTC is commonly used as a translational model to study neurobiological and behavioral aspects of fear and anxiety disorders, including Posttraumatic Stress Disorder (PTSD). Though PTSD is a complex, multi-faceted construct that cannot be fully captured in animals, PTC is a conceptually valid model for...

  14. The use of cognitive enhancers in animal models of fear extinction.

    Science.gov (United States)

    Kaplan, Gary B; Moore, Katherine A

    2011-08-01

    In anxiety disorders, such as posttraumatic stress disorders and phobias, classical conditioning pairs natural (unconditioned) fear-eliciting stimuli with contextual or discrete cues resulting in enduring fear responses to multiple stimuli. Extinction is an active learning process that results in a reduction of conditioned fear responses after conditioned stimuli are no longer paired with unconditioned stimuli. Fear extinction often produces incomplete effects and this highlights the relative permanence of bonds between conditioned stimuli and conditioned fear responses. The animal research literature is rich in its demonstration of cognitive enhancing agents that alter fear extinction. This review specifically examines the fear extinguishing effects of cognitive enhancers that act on gamma-aminobutyric acid (GABA), glutamatergic, cholinergic, adrenergic, dopaminergic, and cannabinoid signaling pathways. It also examines the effects of compounds that alter epigenetic and neurotrophic mechanisms in fear extinction. Of these cognitive enhancers, glutamatergic N-methyl d-aspartate (NMDA) receptor agonists, such as D-cycloserine, have enhanced fear extinction in a context-, dose- and time-dependent manner. Agents that function as glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor agonists, alpha2-adrenergic receptor antagonists (such as yohimbine), neurotrophic factors (brain derived neurotrophic factor or BDNF) and histone deacetylase inhibitors (valproate and sodium butyrate) also improve fear extinction in animals. However, some have anxiogenic effects and their contextual and temporal effects need to be more reliably demonstrated. Various cognitive enhancers produce changes in cortico-amygdala synaptic plasticity through multiple mechanisms and these neural changes enhance fear extinction. We need to better define the changes in neural plasticity produced by these agents in order to develop more effective compounds. In the clinical

  15. Fear extinction and BDNF: translating animal models of PTSD to the clinic.

    Science.gov (United States)

    Andero, R; Ressler, K J

    2012-07-01

    Brain-derived neurotrophic factor (BDNF) is the most studied neurotrophin involved in synaptic plasticity processes that are required for long-term learning and memory. Specifically, BDNF gene expression and activation of its high-affinity tropomyosin-related kinase B (TrkB) receptor are necessary in the amygdala, hippocampus and prefrontal cortex for the formation of emotional memories, including fear memories. Among the psychiatric disorders with altered fear processing, there is post-traumatic stress disorder (PTSD) which is characterized by an inability to extinguish fear memories. Since BDNF appears to enhance extinction of fear, targeting impaired extinction in anxiety disorders such as PTSD via BDNF signalling may be an important and novel way to enhance treatment efficacy. The aim of this review is to provide a translational point of view that stems from findings in the BDNF regulation of synaptic plasticity and fear extinction. In addition, there are different systems that seem to alter fear extinction through BDNF modulation like the endocannabinoid system and the hypothalamic-pituitary adrenal axis. Recent work also finds that the pituitary adenylate cyclase-activating polypeptide and PAC1 receptor, which are upstream of BDNF activation, may be implicated in PTSD. Especially interesting are data that exogenous fear extinction enhancers such as antidepressants, histone deacetylases inhibitors and D-cycloserine, a partial N-methyl d-aspartate agonist, may act through or in concert with the BDNF-TrkB system. Finally, we review studies where recombinant BDNF and a putative TrkB agonist, 7,8-dihydroxyflavone, may enhance extinction of fear. These approaches may lead to novel agents that improve extinction in animal models and eventually humans. PMID:22530815

  16. NMDA receptor blockade in the basolateral amygdala disrupts consolidation of stimulus-reward memory and extinction learning during reinstatement of cocaine-seeking in an animal model of relapse.

    Science.gov (United States)

    Feltenstein, Matthew W; See, Ronald E

    2007-11-01

    Previous research from our laboratory has implicated the basolateral amygdala (BLA) complex in the acquisition and consolidation of cue-cocaine associations, as well as extinction learning, which may regulate the long-lasting control of conditioned stimuli (CS) over drug-seeking behavior. Given the well established role of NMDA glutamate receptor activation in other forms of amygdalar-based learning, we predicted that BLA-mediated drug-cue associative learning would be NMDA receptor dependent. To test this hypothesis, male Sprague-Dawley rats self-administered i.v. cocaine (0.6 mg/kg/infusion) in the absence of explicit CS pairings (2-h sessions, 5 days), followed by a single 1-h classical conditioning (CC) session, during which they received passive infusions of cocaine discretely paired with a light+tone stimulus complex. Following additional cocaine self-administration sessions in the absence of the CS (2-h sessions, 5 days) and extinction training sessions (no cocaine or CS presentation, 2-h sessions, 7 days), the ability of the CS to reinstate cocaine-seeking on three test days was assessed. Rats received bilateral intra-BLA infusions (0.5 microl/hemisphere) of vehicle or the selective NMDA receptor antagonist, 2-amino-5-phosphonovalerate (AP-5), immediately prior to the CC session (acquisition), immediately following the CC session (consolidation), or immediately following reinstatement testing (consolidation of conditioned-cued extinction learning). AP-5 administered before or after CC attenuated subsequent CS-induced reinstatement, whereas AP-5 administered immediately following the first two reinstatement tests impaired the extinction of cocaine-seeking behavior. These results suggest that NMDA receptor-mediated mechanisms within the BLA play a crucial role in the consolidation of drug-CS associations into long-term memories that, in turn, drive cocaine-seeking during relapse. PMID:17613253

  17. Deepened Extinction following Compound Stimulus Presentation: Noradrenergic Modulation

    Science.gov (United States)

    Janak, Patricia H.; Corbit, Laura H.

    2011-01-01

    Behavioral extinction is an active form of new learning involving the prediction of nonreward where reward has previously been present. The expression of extinction learning can be disrupted by the presentation of reward itself or reward-predictive stimuli (reinstatement) as well as the passage of time (spontaneous recovery) or contextual changes…

  18. [Extinction and Reconsolidation of Memory].

    Science.gov (United States)

    Zuzina, A B; Balaban, P M

    2015-01-01

    Retrieval of memory followed by reconsolidation can strengthen a memory, while retrieval followed by extinction results in a decrease of memory performance due to weakening of existing memory or formation of a competing memory. In our study we analyzed the behavior and responses of identified neurons involved in the network underlying aversive learning in terrestrial snail Helix, and made an attempt to describe the conditions in which the retrieval of memory leads either to extinction or reconsolidation. In the network underlying the withdrawal behavior, sensory neurons, premotor interneurons, motor neurons, and modulatory for this network serotonergic neurons are identified and recordings from representatives of these groups were made before and after aversive learning. In the network underlying feeding behavior, the premotor modulatory serotonergic interneurons and motor neurons involved in motor program of feeding are identified. Analysis of changes in neural activity after aversive learning showed that modulatory neurons of feeding behavior do not demonstrate any changes (sometimes a decrease of responses to food was observed), while responses to food in withdrawal behavior premotor interneurons changed qualitatively, from under threshold EPSPs to spike discharges. Using a specific for serotonergic neurons neurotoxin 5,7-DiHT it was shown previously that the serotonergic system is necessary for the aversive learning, but is not necessary for maintenance and retrieval of this memory. These results suggest that the serotonergic neurons that are necessary as part of a reinforcement for developing the associative changes in the network may be not necessary for the retrieval of memory. The hypothesis presented in this review concerns the activity of the "reinforcement" serotonergic neurons that is suggested to be the gate condition for the choice between extinction/reconsolidation triggered by memory retrieval: if these serotonergic neurons do not respond during the

  19. Gradual extinction reduces Reinstatement

    Directory of Open Access Journals (Sweden)

    Youssef eShiban

    2015-09-01

    Full Text Available The current study investigated whether gradually reducing the frequency of aversive stimuli during extinction can prevent the return of fear. Thirty-one participants of a three-stage procedure (acquisition, extinction and a reinstatement test on day two were randomly assigned to a standard extinction (SE and gradual extinction (GE procedure. The two groups differed only in the extinction procedure. While the SE group ran through a regular extinction process without any negative events, the frequency of the aversive stimuli during the extinction phase was gradually reduced for the GE group. The unconditioned stimulus was an air blast (5 bar, 10 ms. A spider and a scorpion were used as conditioned stimuli. The outcome variables were contingency ratings and physiological measures (skin conductance response and startle response. There were no differences found between the two groups for the acquisition and extinction phases concerning contingency ratings, SCR, or startle response. Gradual extinction compared to standard extinction significantly reduced the return of fear in the reinstatement test for the startle response but not for skin conductance response or contingency ratings. This study was successful in translating the findings in rodent to humans. The results suggest that the gradual extinction process is suitable for increasing the efficacy of fear extinction.

  20. Social defeat: impact on fear extinction and amygdala-prefrontal cortical theta synchrony in 5-HTT deficient mice.

    Science.gov (United States)

    Narayanan, Venu; Heiming, Rebecca S; Jansen, Friederike; Lesting, Jörg; Sachser, Norbert; Pape, Hans-Christian; Seidenbecher, Thomas

    2011-01-01

    Emotions, such as fear and anxiety, can be modulated by both environmental and genetic factors. One genetic factor is for example the genetically encoded variation of the serotonin transporter (5-HTT) expression. In this context, the 5-HTT plays a key role in the regulation of central 5-HT neurotransmission, which is critically involved in the physiological regulation of emotions including fear and anxiety. However, a systematic study which examines the combined influence of environmental and genetic factors on fear-related behavior and the underlying neurophysiological basis is missing. Therefore, in this study we used the 5-HTT-deficient mouse model for studying emotional dysregulation to evaluate consequences of genotype specific disruption of 5-HTT function and repeated social defeat for fear-related behaviors and corresponding neurophysiological activities in the lateral amygdala (LA) and infralimbic region of the medial prefrontal cortex (mPFC) in male 5-HTT wild-type (+/+), homo- (-/-) and heterozygous (+/-) mice. Naive males and experienced losers (generated in a resident-intruder paradigm) of all three genotypes, unilaterally equipped with recording electrodes in LA and mPFC, underwent a Pavlovian fear conditioning. Fear memory and extinction of conditioned fear was examined while recording neuronal activity simultaneously with fear-related behavior. Compared to naive 5-HTT+/+ and +/- mice, 5-HTT-/- mice showed impaired recall of extinction. In addition, 5-HTT-/- and +/- experienced losers showed delayed extinction learning and impaired recall of extinction. Impaired behavioral responses were accompanied by increased theta synchronization between the LA and mPFC during extinction learning in 5-HTT-/- and +/- losers. Furthermore, impaired extinction recall was accompanied with increased theta synchronization in 5-HTT-/- naive and in 5-HTT-/- and +/- loser mice. In conclusion, extinction learning and memory of conditioned fear can be modulated by both the 5

  1. Social defeat: impact on fear extinction and amygdala-prefrontal cortical theta synchrony in 5-HTT deficient mice.

    Directory of Open Access Journals (Sweden)

    Venu Narayanan

    Full Text Available Emotions, such as fear and anxiety, can be modulated by both environmental and genetic factors. One genetic factor is for example the genetically encoded variation of the serotonin transporter (5-HTT expression. In this context, the 5-HTT plays a key role in the regulation of central 5-HT neurotransmission, which is critically involved in the physiological regulation of emotions including fear and anxiety. However, a systematic study which examines the combined influence of environmental and genetic factors on fear-related behavior and the underlying neurophysiological basis is missing. Therefore, in this study we used the 5-HTT-deficient mouse model for studying emotional dysregulation to evaluate consequences of genotype specific disruption of 5-HTT function and repeated social defeat for fear-related behaviors and corresponding neurophysiological activities in the lateral amygdala (LA and infralimbic region of the medial prefrontal cortex (mPFC in male 5-HTT wild-type (+/+, homo- (-/- and heterozygous (+/- mice. Naive males and experienced losers (generated in a resident-intruder paradigm of all three genotypes, unilaterally equipped with recording electrodes in LA and mPFC, underwent a Pavlovian fear conditioning. Fear memory and extinction of conditioned fear was examined while recording neuronal activity simultaneously with fear-related behavior. Compared to naive 5-HTT+/+ and +/- mice, 5-HTT-/- mice showed impaired recall of extinction. In addition, 5-HTT-/- and +/- experienced losers showed delayed extinction learning and impaired recall of extinction. Impaired behavioral responses were accompanied by increased theta synchronization between the LA and mPFC during extinction learning in 5-HTT-/- and +/- losers. Furthermore, impaired extinction recall was accompanied with increased theta synchronization in 5-HTT-/- naive and in 5-HTT-/- and +/- loser mice. In conclusion, extinction learning and memory of conditioned fear can be modulated

  2. Estrous cycle phase and gonadal hormones influence conditioned fear extinction

    Science.gov (United States)

    Milad, Mohammed R; Igoe, Sarah A; Lebron-Milad, Kelimer; Novales, Juan E

    2009-01-01

    Gonadal hormones modulate fear acquisition, but less is known about the influence of gonadal hormones on fear extinction. We assessed sex differences and the influence of gonadal hormone fluctuations and exogenous manipulations of estrogen and progesterone on acquisition, extinction learning and extinction recall in a 3-day auditory fear conditioning and extinction protocol. Experiments were conducted on males and naturally cycling female rats. Regarding female rats, significant differences in fear extinction were observed between subgroups of females, depending on their phase of the estrous cycle. Extinction that took place during the proestrus (high estrogen/progesterone) phase was more fully consolidated, as evidenced by low freezing during a recall test. This suggests that estrogen and/or progesterone facilitate extinction. In support of this, injection of both estrogen and progesterone prior to extinction learning in female rats during the metestrus phase of the cycle (low estrogen/progesterone) facilitated extinction consolidation, and blockade of estrogen and progesterone receptors during the proestrus phase impaired extinction consolidation. When comparing male to female rats without consideration of the estrous cycle phase, no significant sex differences were observed. When accounting for cycle phase in females, sex differences were observed only during extinction recall. Female rats that underwent extinction during the metestrus phase showed significantly higher freezing during the recall test relative to males. Collectively, these data suggest that gonadal hormones influence extinction behavior possibly by influencing the function of brain regions involved in the consolidation of fear extinction. Moreover, the elevated fear observed in female relative to male rats during extinction recall suggests that gonadal hormones may in part play a role in the higher prevalence of anxiety disorders in women. PMID:19761818

  3. Supramammillary serotonin reduction alters place learning and concomitant hippocampal, septal, and supramammillar theta activity in a Morris water maze

    Science.gov (United States)

    Hernández-Pérez, J. Jesús; Gutiérrez-Guzmán, Blanca E.; López-Vázquez, Miguel Á.; Olvera-Cortés, María E.

    2015-01-01

    Hippocampal theta activity is related to spatial information processing, and high-frequency theta activity, in particular, has been linked to efficient spatial memory performance. Theta activity is regulated by the synchronizing ascending system (SAS), which includes mesencephalic and diencephalic relays. The supramamillary nucleus (SUMn) is located between the reticularis pontis oralis and the medial septum (MS), in close relation with the posterior hypothalamic nucleus (PHn), all of which are part of this ascending system. It has been proposed that the SUMn plays a role in the modulation of hippocampal theta-frequency; this could occur through direct connections between the SUMn and the hippocampus or through the influence of the SUMn on the MS. Serotonergic raphe neurons prominently innervate the hippocampus and several components of the SAS, including the SUMn. Serotonin desynchronizes hippocampal theta activity, and it has been proposed that serotonin may regulate learning through the modulation of hippocampal synchrony. In agreement with this hypothesis, serotonin depletion in the SUMn/PHn results in deficient spatial learning and alterations in CA1 theta activity-related learning in a Morris water maze. Because it has been reported that SUMn inactivation with lidocaine impairs the consolidation of reference memory, we asked whether changes in hippocampal theta activity related to learning would occur through serotonin depletion in the SUMn, together with deficiencies in memory. We infused 5,7-DHT bilaterally into the SUMn in rats and evaluated place learning in the standard Morris water maze task. Hippocampal (CA1 and dentate gyrus), septal and SUMn EEG were recorded during training of the test. The EEG power in each region and the coherence between the different regions were evaluated. Serotonin depletion in the SUMn induced deficient spatial learning and altered the expression of hippocampal high-frequency theta activity. These results provide evidence in

  4. Cannabinoid facilitation of fear extinction memory recall in humans.

    Science.gov (United States)

    Rabinak, Christine A; Angstadt, Mike; Sripada, Chandra S; Abelson, James L; Liberzon, Israel; Milad, Mohammed R; Phan, K Luan

    2013-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of the cannabinoid system during extinction learning enhances fear extinction and its retention. Specifically, CB1 receptor agonists, such as Δ9-tetrahydrocannibinol (THC), can facilitate extinction recall by preventing recovery of extinguished fear in rats. However, this phenomenon has not been investigated in humans. We conducted a study using a randomized, double-blind, placebo-controlled, between-subjects design, coupling a standard Pavlovian fear extinction paradigm and simultaneous skin conductance response (SCR) recording with an acute pharmacological challenge with oral dronabinol (synthetic THC) or placebo (PBO) 2 h prior to extinction learning in 29 healthy adult volunteers (THC = 14; PBO = 15) and tested extinction retention 24 h after extinction learning. Compared to subjects that received PBO, subjects that received THC showed low SCR to a previously extinguished CS when extinction memory recall was tested 24 h after extinction learning, suggesting that THC prevented the recovery of fear. These results provide the first evidence that pharmacological enhancement of extinction learning is feasible in humans using cannabinoid system modulators, which may thus warrant further development and clinical testing. This article is part of a Special Issue entitled 'Cognitive Enhancers'. PMID:22796109

  5. Secondary extinctions of biodiversity.

    Science.gov (United States)

    Brodie, Jedediah F; Aslan, Clare E; Rogers, Haldre S; Redford, Kent H; Maron, John L; Bronstein, Judith L; Groves, Craig R

    2014-12-01

    Extinctions beget further extinctions when species lose obligate mutualists, predators, prey, or hosts. Here, we develop a conceptual model of species and community attributes affecting secondary extinction likelihood, incorporating mechanisms that buffer organisms against partner loss. Specialized interactors, including 'cryptic specialists' with diverse but nonredundant partner assemblages, incur elevated risk. Risk is also higher for species that cannot either evolve new traits following partner loss or obtain novel partners in communities reorganizing under changing environmental conditions. Partner loss occurs alongside other anthropogenic impacts; multiple stressors can circumvent ecological buffers, enhancing secondary extinction risk. Stressors can also offset each other, reducing secondary extinction risk, a hitherto unappreciated phenomenon. This synthesis suggests improved conservation planning tactics and critical directions for research on secondary extinctions. PMID:25445878

  6. Effects of sleep on memory for conditioned fear and fear extinction

    OpenAIRE

    Pace-Schott, Edward F.; Germain, Anne; Milad, Mohammed R

    2015-01-01

    Learning and memory for extinction of conditioned fear is a basic mammalian mechanism for regulating negative emotion. Sleep promotes both the consolidation of memory and the regulation of emotion. Sleep can influence consolidation and modification of memories associated with both fear and its extinction. After brief overviews of the behavior and neural circuitry associated with fear conditioning, extinction learning and extinction memory in the rodent and human, interactions of sleep with th...

  7. Alteration of Influencing Factors of E-Learning Continued Intention for Different Degrees of Online Participation

    Science.gov (United States)

    Chang, Chi-Cheng; Liang, Chaoyun; Shu, Kuen-Ming; Chiu, Yi-Chun

    2015-01-01

    The purpose of the present study was to investigate the variation of influencing factors of e-learning continuance intention for different degrees of participation and to examine moderating effects of degrees of participation on influencing factors of e-learning continuance intention. Participants included 670 learners from an adult professional…

  8. Extinction of chained instrumental behaviors: Effects of consumption extinction on procurement responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2016-03-01

    Operant behavior is typically organized into sequences of responses that eventually lead to a reinforcer. Response elements can be categorized as those that directly lead to reward consumption (i.e., a consumption response) and those that lead to the opportunity to make the consumption response (i.e., a procurement response). These responses often differ topographically and in terms of the discriminative stimuli that set the occasion for them. We have recently shown that extinction of the procurement response acts to weaken the specific associated consumption response, and that active inhibition of the procurement response is required for this effect. To expand the analysis of the associative structure of chains, in the present experiments we asked the reverse question: whether extinction of consumption behavior results in a decrease in the associated procurement response in a discriminated heterogeneous chain. In Experiment 1, extinction of consumption alone led to an attenuation of the associated procurement response only when rats were allowed to make the consumption response in extinction. Exposure to the consumption stimulus alone was not sufficient to produce weakened procurement responding. In Experiment 2, rats learned two distinct heterogeneous chains, and extinction of one consumption response specifically weakened the procurement response associated with it. The results add to the evidence suggesting that rats learn a highly specific associative structure in behavior chains, emphasizing the role of learning response inhibition in extinction.

  9. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    reasons (certain groups do not fossilize) and methodological problems (methods of excavation and identification). Consequently, we can only crudely estimate the current rate of extinction. Nonetheless, it is evident that humans generated a new mass extinction, affecting all species in all habitats, and...

  10. End Ordovician extinctions

    DEFF Research Database (Denmark)

    Harper, David Alexander Taylor; Hammarlund, Emma U.; Rasmussen, Christian Mac Ørum

    2014-01-01

    -global anoxia associated with a marked transgression during the Late Hirnantian. Most recently, however, new drivers for the extinctions have been proposed, including widespread euxinia together with habitat destruction caused by plate tectonic movements, suggesting that the end Ordovician mass extinctions were...

  11. Altered brain activation in a reversal learning task unmasks adaptive changes in cognitive control in writer's cramp.

    Science.gov (United States)

    Zeuner, Kirsten E; Knutzen, Arne; Granert, Oliver; Sablowsky, Simone; Götz, Julia; Wolff, Stephan; Jansen, Olav; Dressler, Dirk; Schneider, Susanne A; Klein, Christine; Deuschl, Günther; van Eimeren, Thilo; Witt, Karsten

    2016-01-01

    Previous receptor binding studies suggest dopamine function is altered in the basal ganglia circuitry in task-specific dystonia, a condition characterized by contraction of agonist and antagonist muscles while performing specific tasks. Dopamine plays a role in reward-based learning. Using fMRI, this study compared 31 right-handed writer's cramp patients to 35 controls in reward-based learning of a probabilistic reversal-learning task. All subjects chose between two stimuli and indicated their response with their left or right index finger. One stimulus response was rewarded 80%, the other 20%. After contingencies reversal, the second stimulus response was rewarded in 80%. We further linked the DRD2/ANKK1-TaqIa polymorphism, which is associated with 30% reduction of the striatal dopamine receptor density with reward-based learning and assumed impaired reversal learning in A + subjects. Feedback learning in patients was normal. Blood-oxygen level dependent (BOLD) signal in controls increased with negative feedback in the insula, rostral cingulate cortex, middle frontal gyrus and parietal cortex (pFWE negative feedback in the dorsal anterior cingulate cortex (BA32). The genetic status was not correlated with the BOLD activity. The Brodmann area 32 (BA32) is part of the dorsal anterior cingulate cortex (dACC) that plays an important role in coordinating and integrating information to guide behavior and in reward-based learning. The dACC is connected with the basal ganglia-thalamo-loop modulated by dopaminergic signaling. This finding suggests disturbed integration of reinforcement history in decision making and implicate that the reward system might contribute to the pathogenesis in writer's cramp. PMID:26702397

  12. Timing, tempo and paleoenvironmental implications of Deccan volcanism relative to the KTB extinction, what we can learn from the red bole record?

    Science.gov (United States)

    Adatte, Thierry; Sordet, Valentin; Keller, Gerta; Schoene, Blair; Samperton, Kyle; Khadri, Syed

    2016-04-01

    Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (phase-2) occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase-2 began 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. In India a strong floral response is observed as a direct consequence of volcanic phase-2. Shortly after the onset of Deccan phase-2, the floral association dominated by gymnosperms and angiosperms was decimated as indicated by a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions as a direct result of volcanic activity. The inter-trappean sediments deposited in phase-2 are characterized by the highest alteration CIA index values suggesting increased acid rains due to SO2 emissions. In addition, a sharp decrease in pollen and spores coupled with the appearance of fungi mark increasing stress conditions, which are likely a direct result of volcanic activity. Bulk organic geochemistry points to a strong degradation of the indigenous organic matter, suggesting that the biomass was oxidized in acidic conditions triggered by intense volcanic activity. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles that mark quiescent periods between basalt flows. Red boles have increasingly attracted the attention of researchers to understand the climatic and paleoenvironmental impact of Continental Flood Basalts (CFB). Recent advances in U-Pb dating of Deccan lava flows, studies of weathering patterns and paleoclimatic information gained from multiproxy analyses of red bole beds (e.g., lithology, mineralogy, geochemistry) yield crucial evidence of environmental changes

  13. Modeling galactic extinction

    Directory of Open Access Journals (Sweden)

    C. Cecchi-Pestellini

    2011-09-01

    Full Text Available We present a model for interstellar extinction dust, in which we assume a bimodal distribution of extinction carriers, a dispersion of core-mantle grains, supplemented by a collection of PAHs in free molecular form. We use state-of-the-art methods to calculate the extinction due to macroscopic dust particles, and the absorption cross-sections of PAHs in four different charge states. While successfull for most of observed Galactic extinction curves, in few cases the model cannot provide reliable results. Paradoxically, these failures appear to be very promising, suggesting that the whole body of dust extinction features might be described within the cycle of carbon in the interstellar medium.

  14. LDA merging and splitting with applications to multiagent cooperative learning and system alteration.

    Science.gov (United States)

    Pang, Shaoning; Ban, Tao; Kadobayashi, Youki; Kasabov, Nikola K

    2012-04-01

    To adapt linear discriminant analysis (LDA) to real-world applications, there is a pressing need to equip it with an incremental learning ability to integrate knowledge presented by one-pass data streams, a functionality to join multiple LDA models to make the knowledge sharing between independent learning agents more efficient, and a forgetting functionality to avoid reconstruction of the overall discriminant eigenspace caused by some irregular changes. To this end, we introduce two adaptive LDA learning methods: LDA merging and LDA splitting. These provide the benefits of ability of online learning with one-pass data streams, retained class separability identical to the batch learning method, high efficiency for knowledge sharing due to condensed knowledge representation by the eigenspace model, and more preferable time and storage costs than traditional approaches under common application conditions. These properties are validated by experiments on a benchmark face image data set. By a case study on the application of the proposed method to multiagent cooperative learning and system alternation of a face recognition system, we further clarified the adaptability of the proposed methods to complex dynamic learning tasks.

  15. Extinction and the fossil record

    Science.gov (United States)

    Sepkoski, J. J. Jr; Sepkoski JJ, ,. J. r. (Principal Investigator)

    1994-01-01

    The author examines evidence of mass extinctions in the fossil record and searches for reasons for such large extinctions. Five major mass extinctions eliminated at least 40 percent of animal genera in the oceans and from 65 to 95 percent of ocean species. Questions include the occurrence of gradual or catastrophic extinctions, causes, environment, the capacity of a perturbation to cause extinctions each time it happens, and the possibility and identification of complex events leading to a mass extinction.

  16. Visual Learning Alters the Spontaneous Activity of the Resting Human Brain: An fNIRS Study

    OpenAIRE

    Haijing Niu; Hao Li; Li Sun; Yongming Su; Jing Huang; Yan Song

    2014-01-01

    Resting-state functional connectivity (RSFC) has been widely used to investigate spontaneous brain activity that exhibits correlated fluctuations. RSFC has been found to be changed along the developmental course and after learning. Here, we investigated whether and how visual learning modified the resting oxygenated hemoglobin (HbO) functional brain connectivity by using functional near-infrared spectroscopy (fNIRS). We demonstrate that after five days of training on an orientation discrimina...

  17. Extinction debt in source-sink metacommunities.

    Directory of Open Access Journals (Sweden)

    Nicolas Mouquet

    Full Text Available In an increasingly modified world, understanding and predicting the consequences of landscape alteration on biodiversity is a challenge for ecologists. To this end, metacommunity theory has developed to better understand the complexity of local and regional interactions that occur across larger landscapes. While metacommunity ecology has now provided several alternative models of species coexistence at different spatial scales, predictions regarding the consequences of landscape alteration have been done exclusively for the competition-colonization trade off model (CC. In this paper we investigate the effects of landscape perturbation on source-sink metacommunities. We show that habitat destruction perturbs the equilibria among species competitive effects within the metacommunity, driving both direct extinctions and an indirect extinction debt. As in CC models, we found a time lag for extinction following habitat destruction that varied in length depending upon the relative importance of direct and indirect effects. However, in contrast to CC models, we found that the less competitive species are more affected by habitat destruction. The best competitors can sometimes even be positively affected by habitat destruction, which corresponds well with the results of field studies. Our results are complementary to those results found in CC models of metacommunity dynamics. From a conservation perspective, our results illustrate that landscape alteration jeopardizes species coexistence in patchy landscapes through complex indirect effects and delayed extinctions patterns.

  18. Tyrosinemia type I and not treatment with NTBC causes slower learning and altered behavior in mice.

    Science.gov (United States)

    Hillgartner, Megan A; Coker, Sarah B; Koenig, Ashton E; Moore, Marissa E; Barnby, Elizabeth; MacGregor, Gordon G

    2016-09-01

    Tyrosinemia type I is a recessive inborn error of metabolism caused by mutations in the fumarylacetoacetate hydrolase (FAH) gene, coding for the final enzyme in the metabolism of tyrosine. This renders FAH nonfunctional and without treatment, toxic metabolites accumulate causing liver and kidney damage. Introduction of the drug NTBC in 2002 offered a treatment which inhibits an upstream enzyme, preventing the production of the toxic metabolites. There is now a long-term survival rate of greater than 90 % in children, but there are reports of lower cognitive function and IQ as well as schooling and behavioral problems in these children. We studied a mouse model of tyrosinemia type I to gain insight into the effects of tyrosinemia type I and treatment with NTBC on mouse learning, memory, and behavior. In the Barnes maze, visual and spatial cues can be used by mice to remember the location of a dark escape box. The primary time, distance, and strategy taken by the mice to locate the escape box is a measure of learning and memory. Our findings show that mice with tyrosinemia type I were slower to learn than wild-type mice treated with NTBC and made more mistakes, but were capable of learning and storing long-term memory. After learning the location of the target hole, mice with tyrosinemia type I respond differently to a change in location and were less flexible in learning the new target hole location. Our findings suggest that this slower learning and cognitive difference is caused by tyrosinemia type I and not by the treatment with NTBC. PMID:27271696

  19. [GABA-Receptors in Modulation of Fear Memory Extinction].

    Science.gov (United States)

    Dubrovina, N I

    2016-01-01

    GABA is the major inhibitory neurotransmitter in the central nervous system determining the efficacy of neuronal interaction. GABA-receptors play a key role in different aspects of fear memory--acquisition and consolidation, retention, reconsolidation and extinction. Extinction is an important behavioural phenomenon which allows organism to adapt its behavior to a changing environment. Extinction of fear memory is a form of new inhibitory learning which interferes with expression of the initial acquired fear conditioning. Resistance to extinction is symptom of depression and posttraumatic stress disorder. The aim of the present review was to summarize own and literary data about GABAergic modulation of fear extinction and pharmacological correction of extinction impairment at influences on GABA(A)- and GABA(B)- receptors. PMID:27538279

  20. Severely impaired learning and altered neuronal morphology in mice lacking NMDA receptors in medium spiny neurons.

    Directory of Open Access Journals (Sweden)

    Lisa R Beutler

    Full Text Available The striatum is composed predominantly of medium spiny neurons (MSNs that integrate excitatory, glutamatergic inputs from the cortex and thalamus, and modulatory dopaminergic inputs from the ventral midbrain to influence behavior. Glutamatergic activation of AMPA, NMDA, and metabotropic receptors on MSNs is important for striatal development and function, but the roles of each of these receptor classes remain incompletely understood. Signaling through NMDA-type glutamate receptors (NMDARs in the striatum has been implicated in various motor and appetitive learning paradigms. In addition, signaling through NMDARs influences neuronal morphology, which could underlie their role in mediating learned behaviors. To study the role of NMDARs on MSNs in learning and in morphological development, we generated mice lacking the essential NR1 subunit, encoded by the Grin1 gene, selectively in MSNs. Although these knockout mice appear normal and display normal 24-hour locomotion, they have severe deficits in motor learning, operant conditioning and active avoidance. In addition, the MSNs from these knockout mice have smaller cell bodies and decreased dendritic length compared to littermate controls. We conclude that NMDAR signaling in MSNs is critical for normal MSN morphology and many forms of learning.

  1. Role of Medial Prefrontal Cortex Narp in the Extinction of Morphine Conditioned Place Preference

    Science.gov (United States)

    Blouin, Ashley M.; Han, Sungho; Pearce, Anne M.; Cheng, KaiLun; Lee, JongAh J.; Johnson, Alexander W.; Wang, Chuansong; During, Matthew J.; Holland, Peter C.; Shaham, Yavin; Baraban, Jay M.; Reti, Irving M.

    2013-01-01

    Narp knockout (KO) mice demonstrate an impaired extinction of morphine conditioned place preference (CPP). Because the medial prefrontal cortex (mPFC) has been implicated in extinction learning, we tested whether Narp cells in this region play a role in the extinction of morphine CPP. We found that intracranial injections of adenoassociated virus…

  2. All about Endangered and Extinct Animals. Animal Life for Children. [Videotape].

    Science.gov (United States)

    2000

    While there are thousands of different animals in the world, some have been extinct for many years and others are on the verge of extinction. In this videotape, students learn about the natural and man-made factors that lead to the endangerment and extinction of animals. Children find out why it is essential for people to help all forms of…

  3. Differential Regulation of Glutamic Acid Decarboxylase Gene Expression after Extinction of a Recent Memory vs. Intermediate Memory

    Science.gov (United States)

    Sangha, Susan; Ilenseer, Jasmin; Sosulina, Ludmila; Lesting, Jorg; Pape, Hans-Christian

    2012-01-01

    Extinction reduces fear to stimuli that were once associated with an aversive event by no longer coupling the stimulus with the aversive event. Extinction learning is supported by a network comprising the amygdala, hippocampus, and prefrontal cortex. Previous studies implicate a critical role of GABA in extinction learning, specifically the GAD65…

  4. Delayed extinction and stronger drug-primed reinstatement of methamphetamine seeking in rats prenatally exposed to morphine.

    Science.gov (United States)

    Shen, Ying-Ling; Chen, Shao-Tsu; Chan, Tzu-Yi; Hung, Tsai-Wei; Tao, Pao-Luh; Liao, Ruey-Ming; Chan, Ming-Huan; Chen, Hwei-Hsien

    2016-02-01

    Prenatal morphine (PM) affects the development of brain reward system and cognitive function. The present study aimed to determine whether PM exposure increases the vulnerability to MA addiction. Pregnant Sprague-Dawley rats were administered saline or morphine during embryonic days 3-20. The acquisition, extinction and reinstatement of methamphetamine (MA) conditioned place preference (CPP) and intravenous self-administration (SA) paradigms were assessed in the male adult offspring. There was no difference in the acquisition and expression of MA CPP between saline- and PM-exposed rats, whereas PM-exposed rats exhibited slower extinction and greater MA priming-induced reinstatement of drug-seeking behavior than controls. Similarly, MA SA under progressive ratio and fixed ratio schedules was not affected by PM exposure, but PM-exposed rats required more extinction sessions to reach the extinction criteria and displayed more severe MA priming-, but not cue-induced, reinstatement. Such alterations in extinction and reinstatement were not present when PM-exposed rats were tested in an equivalent paradigm assessing operant responding for food pellets. Our results demonstrate that PM exposure did not affect the association memory formation during acquisition of MA CPP or SA, but impaired extinction learning and increased MA-primed reinstatement in both tasks. These findings suggest that the offspring of women using morphine or heroin during pregnancy might predict persistent MA seeking during extinction and enhanced propensity to MA relapse although they might not be more susceptible to the reinforcing effect of MA during initiation of drug use. PMID:26743042

  5. Removal of Positive Reinforcement to Alter Learning Disabled Adolescents' Preacademic Problems.

    Science.gov (United States)

    Swanson, Lee

    1979-01-01

    One reversal and two multiple baseline designs were used to assess the effects of punishment on the disruptive behavior of six adolescent learning disability students. During baseline conditions of praise and ignore contingencies, the frequency of inappropriate preacademic behavior was assessed. With the institution of punishment procedures,…

  6. Cholinergic Modulation during Acquisition of Olfactory Fear Conditioning Alters Learning and Stimulus Generalization in Mice

    Science.gov (United States)

    Pavesi, Eloisa; Gooch, Allison; Lee, Elizabeth; Fletcher, Max L.

    2013-01-01

    We investigated the role of cholinergic neurotransmission in olfactory fear learning. Mice receiving pairings of odor and foot shock displayed fear to the trained odor the following day. Pretraining injections of the nicotinic antagonist mecamylamine had no effect on subsequent freezing, while the muscarinic antagonist scopolamine significantly…

  7. Dopamine DRD2 polymorphism alters reversal learning and associated neural activity

    NARCIS (Netherlands)

    Jocham, G.; Klein, T.A.; Neumann, J.; Cramon, D.Y. von; Reuter, M.; Ullsperger, M.

    2009-01-01

    In humans, presence of an A1 allele of the DRD2/ANKK1-TaqIa polymorphism is associated with reduced expression of dopamine (DA) D-2 receptors in the striatum. Recently, it was observed that carriers of the A1 allele (A1 + subjects) showed impaired learning from negative feedback in a reinforcement l

  8. Extinction of oscillating populations.

    Science.gov (United States)

    Smith, Naftali R; Meerson, Baruch

    2016-03-01

    Established populations often exhibit oscillations in their sizes that, in the deterministic theory, correspond to a limit cycle in the space of population sizes. If a population is isolated, the intrinsic stochasticity of elemental processes can ultimately bring it to extinction. Here we study extinction of oscillating populations in a stochastic version of the Rosenzweig-MacArthur predator-prey model. To this end we develop a WKB (Wentzel, Kramers and Brillouin) approximation to the master equation, employing the characteristic population size as the large parameter. Similar WKB theories have been developed previously in the context of population extinction from an attracting multipopulation fixed point. We evaluate the extinction rates and find the most probable paths to extinction from the limit cycle by applying Floquet theory to the dynamics of an effective four-dimensional WKB Hamiltonian. We show that the entropic barriers to extinction change in a nonanalytic way as the system passes through the Hopf bifurcation. We also study the subleading pre-exponential factors of the WKB approximation. PMID:27078294

  9. Impaired water maze learning performance without altered dopaminergic function in mice heterozygous for the GDNF mutation.

    Science.gov (United States)

    Gerlai, R; McNamara, A; Choi-Lundberg, D L; Armanini, M; Ross, J; Powell-Braxton, L; Phillips, H S

    2001-10-01

    Exogenous glial cell line-derived neurotrophic factor (GDNF) exhibits potent survival-promoting effects on dopaminergic neurons of the nigrostriatal pathway that is implicated in Parkinson's disease and also protects neurons in forebrain ischemia of animal models. However, a role for endogenous GDNF in brain function has not been established. Although mice homozygous for a targeted deletion of the GDNF gene have been generated, these mice die within hours of birth because of deficits in kidney morphogenesis, and, thus, the effect of the absence of GDNF on brain function could not be studied. Herein, we sought to determine whether adult mice, heterozygous for a GDNF mutation on two different genetic backgrounds, demonstrate alterations in the nigrostriatal dopaminergic system or in cognitive function. While both neurochemical and behavioural measures suggested that reduction of GDNF gene expression in the mutant mice does not alter the nigrostriatal dopaminergic system, it led to a significant and selective impairment of performance in the spatial version of the Morris water maze. A standard panel of blood chemistry tests and basic pathological analyses did not reveal alterations in the mutants that could account for the observed performance deficit. These results suggest that endogenous GDNF may not be critical for the development and functioning of the nigrostriatal dopaminergic system but it plays an important role in cognitive abilities. PMID:11683907

  10. Extinction of chained instrumental behaviors: Effects of procurement extinction on consumption responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2015-07-01

    Instrumental behavior often consists of sequences or chains of responses that minimally include procurement behaviors that enable subsequent consumption behaviors. In such chains, behavioral units are linked by access to one another and eventually to a primary reinforcer, such as food or a drug. The present experiments examined the effects of extinguishing procurement responding on consumption responding after training of a discriminated heterogeneous instrumental chain. Rats learned to make a procurement response (e.g., pressing a lever) in the presence of a distinctive discriminative stimulus; making that response led to the presentation of a second discriminative stimulus that set the occasion for a consumption response (e.g., pulling a chain), which then produced a food-pellet reinforcer. Experiment 1 showed that extinction of either the full procurement-consumption chain or procurement alone weakened the consumption response tested in isolation. Experiment 2 replicated the procurement extinction effect and further demonstrated that the opportunity to make the procurement response, as opposed to simple exposure to the procurement stimulus alone, was required. In Experiment 3, rats learned 2 distinct discriminated heterogeneous chains; extinction of 1 procurement response specifically weakened the consumption response that had been associated with it. The results suggest that learning to inhibit the procurement response may produce extinction of consumption responding through mediated extinction. The experiments suggest the importance of an associative analysis of instrumental behavior chains. (PsycINFO Database Record

  11. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids.

    Science.gov (United States)

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-05-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders. PMID:26514583

  12. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids

    Science.gov (United States)

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-01-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders. PMID:26514583

  13. Light extinction in the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Laulainen, N.

    1992-06-01

    Atmospheric aerosol particles originating from natural sources, such as volcanos and sulfur-bearing gas emissions from the oceans, and from human sources, such as sulfur emissions from fossil fuel combustion and biomass burning, strongly affect visual air quality and are suspected to significantly affect radiative climate forcing of the planet. During the daytime, aerosols obscure scenic vistas, while at night they diminish our ability to observe stellar objects. Scattering of light is the main means by which aerosols attenuate and redistribute light in the atmosphere and by which aerosols can alter and reduce visibility and potentially modify the energy balance of the planet. Trends and seasonal variability of atmospheric aerosol loading, such as column-integrated light extinction or optical depth, and how they may affect potential climate change have been difficult to quantify because there have been few observations made of important aerosol optical parameters, such as optical depth, over the globe and over time and often these are of uneven quality. To address questions related to possible climate change, there is a pressing need to acquire more high-quality aerosol optical depth data. Extensive deployment of improved solar radiometers over the next few years will provide higher-quality extinction data over a wider variety of locations worldwide. An often overlooked source of turbidity data, however, is available from astronomical observations, particularly stellar photoelectric photometry observations. With the exception of the Project ASTRA articles published almost 20 years ago, few of these data ever appear in the published literature. This paper will review the current status of atmospheric extinction observations, as highlighted by the ASTRA work and augmented by more recent solar radiometry measurements.

  14. The role of the medial prefrontal cortex in trace fear extinction

    OpenAIRE

    Kwapis, Janine L.; Jarome, Timothy J.; Fred J Helmstetter

    2015-01-01

    The extinction of delay fear conditioning relies on a neural circuit that has received much attention and is relatively well defined. Whether this established circuit also supports the extinction of more complex associations, however, is unclear. Trace fear conditioning is a better model of complex relational learning, yet the circuit that supports extinction of this memory has received very little attention. Recent research has indicated that trace fear extinction requires a different neural...

  15. Context-dependent human extinction memory is mediated by a ventromedial prefrontal and hippocampal network

    OpenAIRE

    Kalisch, R; Korenfeld, E; Stephan, K E; Weiskopf, N.; Seymour, B.; Dolan, R. J.

    2006-01-01

    In fear extinction, an animal learns that a conditioned stimulus (CS) no longer predicts a noxious stimulus [unconditioned stimulus (UCS)] to which it had previously been associated, leading to inhibition of the conditioned response (CR). Extinction creates a new CS-noUCS memory trace, competing with the initial fear (CS-UCS) memory. Recall of extinction memory and, hence, CR inhibition at later CS encounters is facilitated by contextual stimuli present during extinction training. In line wit...

  16. The Memory System Engaged During Acquisition Determines the Effectiveness of Different Extinction Protocols

    OpenAIRE

    Jarid eGoodman; Mark ePackard

    2015-01-01

    Previous research indicates that extinction of rodent maze behavior may occur without explicit performance of the previously required response. In latent extinction, confining an animal to a previously rewarded goal location without reinforcement is typically sufficient to produce extinction of maze learning. However, previous studies have not determined whether latent extinction may be successfully employed to extinguish all types of memory acquired in the maze, or whether only specific typ...

  17. Disruption of Broca's Area Alters Higher-order Chunking Processing during Perceptual Sequence Learning.

    Science.gov (United States)

    Alamia, Andrea; Solopchuk, Oleg; D'Ausilio, Alessandro; Van Bever, Violette; Fadiga, Luciano; Olivier, Etienne; Zénon, Alexandre

    2016-03-01

    Because Broca's area is known to be involved in many cognitive functions, including language, music, and action processing, several attempts have been made to propose a unifying theory of its role that emphasizes a possible contribution to syntactic processing. Recently, we have postulated that Broca's area might be involved in higher-order chunk processing during implicit learning of a motor sequence. Chunking is an information-processing mechanism that consists of grouping consecutive items in a sequence and is likely to be involved in all of the aforementioned cognitive processes. Demonstrating a contribution of Broca's area to chunking during the learning of a nonmotor sequence that does not involve language could shed new light on its function. To address this issue, we used offline MRI-guided TMS in healthy volunteers to disrupt the activity of either the posterior part of Broca's area (left Brodmann's area [BA] 44) or a control site just before participants learned a perceptual sequence structured in distinct hierarchical levels. We found that disruption of the left BA 44 increased the processing time of stimuli representing the boundaries of higher-order chunks and modified the chunking strategy. The current results highlight the possible role of the left BA 44 in building up effector-independent representations of higher-order events in structured sequences. This might clarify the contribution of Broca's area in processing hierarchical structures, a key mechanism in many cognitive functions, such as language and composite actions. PMID:26765778

  18. Extinction reverses olfactory fear-conditioned increases in neuron number and glomerular size.

    Science.gov (United States)

    Morrison, Filomene G; Dias, Brian G; Ressler, Kerry J

    2015-10-13

    Although much work has investigated the contribution of brain regions such as the amygdala, hippocampus, and prefrontal cortex to the processing of fear learning and memory, fewer studies have examined the role of sensory systems, in particular the olfactory system, in the detection and perception of cues involved in learning and memory. The primary sensory receptive field maps of the olfactory system are exquisitely organized and respond dynamically to cues in the environment, remaining plastic from development through adulthood. We have previously demonstrated that olfactory fear conditioning leads to increased odorant-specific receptor representation in the main olfactory epithelium and in glomeruli within the olfactory bulb. We now demonstrate that olfactory extinction training specific to the conditioned odor stimulus reverses the conditioning-associated freezing behavior and odor learning-induced structural changes in the olfactory epithelium and olfactory bulb in an odorant ligand-specific manner. These data suggest that learning-induced freezing behavior, structural alterations, and enhanced neural sensory representation can be reversed in adult mice following extinction training.

  19. Effects of sleep on memory for conditioned fear and fear extinction.

    Science.gov (United States)

    Pace-Schott, Edward F; Germain, Anne; Milad, Mohammed R

    2015-07-01

    Learning and memory for extinction of conditioned fear is a basic mammalian mechanism for regulating negative emotion. Sleep promotes both the consolidation of memory and the regulation of emotion. Sleep can influence consolidation and modification of memories associated with both fear and its extinction. After brief overviews of the behavior and neural circuitry associated with fear conditioning, extinction learning, and extinction memory in the rodent and human, interactions of sleep with these processes will be examined. Animal and human studies suggest that sleep can serve to consolidate both fear and extinction memory. In humans, sleep also promotes generalization of extinction memory. Time-of-day effects on extinction learning and generalization are also seen. Rapid eye movement (REM) may be a sleep stage of particular importance for the consolidation of both fear and extinction memory as evidenced by selective REM deprivation experiments. REM sleep is accompanied by selective activation of the same limbic structures implicated in the learning and memory of fear and extinction. Preliminary evidence also suggests extinction learning can take place during slow wave sleep. Study of low-level processes such as conditioning, extinction, and habituation may allow sleep effects on emotional memory to be identified and inform study of sleep's effects on more complex, emotionally salient declarative memories. Anxiety disorders are marked by impairments of both sleep and extinction memory. Improving sleep quality may ameliorate anxiety disorders by strengthening naturally acquired extinction. Strategically timed sleep may be used to enhance treatment of anxiety by strengthening therapeutic extinction learned via exposure therapy. (PsycINFO Database Record PMID:25894546

  20. The transition from memory retrieval to extinction

    Directory of Open Access Journals (Sweden)

    Cammarota Martín

    2004-01-01

    Full Text Available Memory is measured by measuring retrieval. Retrieval is often triggered by the conditioned stimulus (CS; however, as known since Pavlov, presentation of the CS alone generates extinction. One-trial avoidance (IA is a much used conditioned fear paradigm in which the CS is the safe part of a training apparatus, the unconditioned stimulus (US is a footshock and the conditioned response is to stay in the safe area. In IA, retrieval is measured without the US, as latency to step-down from the safe area (i.e., a platform. Extinction is installed at the moment of the first unreinforced test session, as clearly shown by the fact that many drugs, including PKA, ERK and protein synthesis inhibitors as well as NMDA receptor antagonists, hinder extinction when infused into the hippocampus or the basolateral amygdala at the moment of the first test session but not later. Some, but not all the molecular systems required for extinction are also activated by retrieval, further endorsing the hypothesis that although retrieval is behaviorally and biochemically necessary for the generation of extinction, this last process constitutes a new learning secondary to the unreinforced expression of the original trace.

  1. Hybridization and extinction.

    Science.gov (United States)

    Todesco, Marco; Pascual, Mariana A; Owens, Gregory L; Ostevik, Katherine L; Moyers, Brook T; Hübner, Sariel; Heredia, Sylvia M; Hahn, Min A; Caseys, Celine; Bock, Dan G; Rieseberg, Loren H

    2016-08-01

    Hybridization may drive rare taxa to extinction through genetic swamping, where the rare form is replaced by hybrids, or by demographic swamping, where population growth rates are reduced due to the wasteful production of maladaptive hybrids. Conversely, hybridization may rescue the viability of small, inbred populations. Understanding the factors that contribute to destructive versus constructive outcomes of hybridization is key to managing conservation concerns. Here, we survey the literature for studies of hybridization and extinction to identify the ecological, evolutionary, and genetic factors that critically affect extinction risk through hybridization. We find that while extinction risk is highly situation dependent, genetic swamping is much more frequent than demographic swamping. In addition, human involvement is associated with increased risk and high reproductive isolation with reduced risk. Although climate change is predicted to increase the risk of hybridization-induced extinction, we find little empirical support for this prediction. Similarly, theoretical and experimental studies imply that genetic rescue through hybridization may be equally or more probable than demographic swamping, but our literature survey failed to support this claim. We conclude that halting the introduction of hybridization-prone exotics and restoring mature and diverse habitats that are resistant to hybrid establishment should be management priorities. PMID:27468307

  2. Predation effects on mean time to extinction under demographic stochasticity.

    Science.gov (United States)

    Palamara, Gian Marco; Delius, Gustav W; Smith, Matthew J; Petchey, Owen L

    2013-10-01

    Methods for predicting the probability and timing of a species' extinction are typically based on single species population dynamics. Assessments of extinction risk often lack effects of interspecific interactions. We study a birth and death process in which the death rate includes an effect of predation. Predation is included via a general nonlinear expression for the functional response of predation to prey density. We investigate the effects of the foraging parameters (e.g. attack rate and handling time) on the mean time to extinction. Mean time to extinction varies by orders of magnitude when we alter the foraging parameters, even when we exclude the effects of these parameters on the equilibrium population size. Conclusions are robust to assumptions about initial conditions and variable predator abundance. These findings clearly show that accounting for the nature of interspecific interactions is likely to be critically important when estimating extinction risk.

  3. Learning, memory and long-term potentiation are altered in Nedd4 heterozygous mice.

    Science.gov (United States)

    Camera, Daria; Coleman, Harold A; Parkington, Helena C; Jenkins, Trisha A; Pow, David V; Boase, Natasha; Kumar, Sharad; Poronnik, Philip

    2016-04-15

    The consolidation of short-term memory into long-term memory involves changing protein level and activity for the synaptic plasticity required for long-term potentiation (LTP). AMPA receptor trafficking is a key determinant of LTP and recently ubiquitination by Nedd4 has been shown to play an important role via direct action on the GluA1 subunit, although the physiological relevance of these findings are yet to be determined. We therefore investigated learning and memory in Nedd4(+/-) mice that have a 50% reduction in levels of Nedd4. These mice showed decreased long-term spatial memory as evidenced by significant increases in the time taken to learn the location of and subsequently find a platform in the Morris water maze. In contrast, there were no significant differences between Nedd4(+/+) and Nedd4(+/-) mice in terms of short-term spatial memory in a Y-maze test. Nedd4(+/-) mice also displayed a significant reduction in post-synaptic LTP measured in hippocampal brain slices. Immunofluorescence of Nedd4 in the hippocampus confirmed its expression in hippocampal neurons of the CA1 region. These findings indicate that reducing Nedd4 protein by 50% significantly impairs LTP and long-term memory thereby demonstrating an important role for Nedd4 in these processes.

  4. Biological Extinction in Earth History

    Science.gov (United States)

    Raup, David M.

    1986-03-01

    Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

  5. Transforming growth factor-β and breast cancer: Lessons learned from genetically altered mouse models

    International Nuclear Information System (INIS)

    Transforming growth factor (TGF)-βs are plausible candidate tumor suppressors in the breast. They also have oncogenic activities under certain circumstances, however. Genetically altered mouse models provide powerful tools to analyze the complexities of TGF-βaction in the context of the whole animal. Overexpression of TGF-β can suppress tumorigenesis in the mammary gland, raising the possibility that use of pharmacologic agents to enhance TGF-β function locally might be an effective method for the chemoprevention of breast cancer. Conversely, loss of TGF-β response increases spontaneous and induced tumorigenesis in the mammary gland. This confirms that endogenous TGF-βs have tumor suppressor activity in the mammary gland, and suggests that the loss of TGF-β receptors seen in some human breast hyperplasias may play a causal role in tumor development

  6. La evaluación de la persistencia basada en una tarea (The assessment of persistence based on an acquisition-extinction learning task

    Directory of Open Access Journals (Sweden)

    José Manuel Hernández López

    2011-04-01

    Full Text Available The aim of the present study was to design an objective task to assess persistence as a personality variable. The conditions for assessing behavioral persistence were analyzed according to the concepts of motivational persistence, obstinate persistence and exploratory persistence. A free operant procedure with an acquisition and an extinction phase was used as a possible context for assessing persistence. The results show that the designed task enabled the measurement of the three variables of persistence in the sample studied. Internal consistency indexes were .928 for motivational persistence, .683 and .580 for the two indicators of obstinate persistence, and .905 for exploratory persistence. The relationships between each persistence variable and the initial motivation of the participants are consistent with those described in the literature.

  7. Ecological model of extinctions

    CERN Document Server

    Abramson, G

    1997-01-01

    We present numerical results based on a simplified ecological system in evolution, showing features of extinction similar to that claimed for the biosystem on Earth. In the model each species consists of a population in interaction with the others, that reproduces and evolves in time. Each species is simultaneously a predator and a prey in a food chain. Mutations that change the interactions are supposed to occur randomly at a low rate. Extinctions of populations result naturally from the predator-prey dynamics. The model is not pinned in a fitness variable, and natural selection arises from the dynamics.

  8. A mouse model of visual perceptual learning reveals alterations in neuronal coding and dendritic spine density in the visual cortex

    Directory of Open Access Journals (Sweden)

    Yan eWang

    2016-03-01

    Full Text Available Visual perceptual learning (VPL can improve spatial vision in normally sighted and visually impaired individuals. Although previous studies of humans and large animals have explored the neural basis of VPL, elucidation of the underlying cellular and molecular mechanisms remains a challenge. Owing to the advantages of molecular genetic and optogenetic manipulations, the mouse is a promising model for providing a mechanistic understanding of VPL. Here, we thoroughly evaluated the effects and properties of VPL on spatial vision in C57BL/6J mice using a two-alternative, forced-choice visual water task. Briefly, the mice underwent prolonged training at near the individual threshold of contrast or spatial frequency (SF for pattern discrimination or visual detection for 35 consecutive days. Following training, the contrast-threshold trained mice showed an 87% improvement in contrast sensitivity (CS and a 55% gain in visual acuity (VA. Similarly, the SF-threshold trained mice exhibited comparable and long-lasting improvements in VA and significant gains in CS over a wide range of SFs. Furthermore, learning largely transferred across eyes and stimulus orientations. Interestingly, learning could transfer from a pattern discrimination task to a visual detection task, but not vice versa. We validated that this VPL fully restored VA in adult amblyopic mice and old mice. Taken together, these data indicate that mice, as a species, exhibit reliable VPL. Intrinsic signal optical imaging revealed that mice with perceptual training had higher cut-off SFs in primary visual cortex (V1 than those without perceptual training. Moreover, perceptual training induced an increase in the dendritic spine density in layer 2/3 pyramidal neurons of V1. These results indicated functional and structural alterations in V1 during VPL. Overall, our VPL mouse model will provide a platform for investigating the neurobiological basis of VPL.

  9. Effects of altered loading states on muscle plasticity: what have we learned from rodents?

    Science.gov (United States)

    Baldwin, K. M.

    1996-01-01

    This paper summarizes the key findings concerning the adaptive properties of rodent muscle in response to altered loading states. When the mechanical stress on the muscle is chronically increased, the muscle adapts by hypertrophying its fibers. This response is regulated by processes resulting in contractile protein expression reflecting slower phenotypes, thereby enabling the muscle to better support load-hearing activity. In contrast, reducing the load-bearing activity induces an opposite response whereby muscles used for both antigravity function and locomotion atrophy while transforming some of the slow fibers into faster contractile phenotypes. Accompanying the atrophy is both a reduced power generating and activity sustaining capability. These adaptive processes are regulated by both transcriptional and translational processes. Available evidence further suggests that the interaction of heavy resistance activity and hormonal/growth factors (insulin-like growth factor, growth hormone, glucocorticoids, etc.) are critical in the maintenance of muscle mass and function. Also resistance training, in contrast to other activities such as endurance running, provides a more economical form of stress because less mechanical activity is required to maintain muscle homeostasis in the context of chronic states of weightlessness.

  10. Differential Endocannabinoid Regulation of Extinction in Appetitive and Aversive Barnes Maze Tasks

    Science.gov (United States)

    Harloe, John P.; Thorpe, Andrew J.; Lichtman, Aron H.

    2008-01-01

    CB[subscript 1] receptor-compromised animals show profound deficits in extinguishing learned behavior from aversive conditioning tasks, but display normal extinction learning in appetitive operant tasks. However, it is difficult to discern whether the differential involvement of the endogenous cannabinoid system on extinction results from the…

  11. Inactivation of the Infralimbic but Not the Prelimbic Cortex Impairs Consolidation and Retrieval of Fear Extinction

    Science.gov (United States)

    Laurent, Vincent; Westbrook, R. Frederick

    2009-01-01

    Rats were subjected to one or two cycles of context fear conditioning and extinction to study the roles of the prelimbic cortex (PL) and infralimbic cortex (IL) in learning and relearning to inhibit fear responses. Inactivation of the PL depressed fear responses across the first or second extinction but did not impair learning or relearning fear…

  12. Fear Extinction in Rodents

    OpenAIRE

    Chang, Chun-hui; Knapska, Ewelina; Orsini, Caitlin A.; Rabinak, Christine A.; Zimmerman, Joshua M; Maren, Stephen

    2009-01-01

    Pavlovian conditioning paradigms have become important model systems for understanding the neuroscience of behavior. In particular, studies of the extinction of Pavlovian fear responses are yielding important information about the neural substrates of anxiety disorders in humans. These studies are germane to understanding the neural mechanisms underlying behavioral interventions that suppress fear, including exposure therapy. This chapter described detailed behavioral protocols for examining ...

  13. The influence of gonadal hormones on conditioned fear extinction in healthy humans.

    Science.gov (United States)

    Milad, M R; Zeidan, M A; Contero, A; Pitman, R K; Klibanski, A; Rauch, S L; Goldstein, J M

    2010-07-14

    Recent rodent studies suggest that gonadal hormones influence extinction of conditioned fear. Here we investigated sex differences in, and the influence of estradiol and progesterone on, fear extinction in healthy humans. Men and women underwent a two-day paradigm in which fear conditioning and extinction learning took place on day 1 and extinction recall was tested on day 2. Visual cues were used as the conditioned stimuli and a mild electric shock was used as the unconditioned stimulus. Skin conductance was recorded throughout the experiment and used to measure conditioned responses (CRs). Blood samples were obtained from all women to measure estradiol and progesterone levels. We found that higher estradiol during extinction learning enhanced subsequent extinction recall but had no effects on fear acquisition or extinction learning itself. Sex differences were only observed during acquisition, with men exhibiting significantly higher CRs. After dividing women into low- and high-estradiol groups, men showed comparable extinction recall to high-estradiol women, and both of these groups showed higher extinction recall than low-estradiol women. Therefore, sex differences in extinction memory emerged only after taking into account women's estradiol levels. Lower estradiol may impair extinction consolidation in women. These findings could have practical applications in the treatment of anxiety disorders through cognitive and behavioral therapies. PMID:20412837

  14. Ecology: Dynamics of Indirect Extinction.

    Science.gov (United States)

    Montoya, Jose M

    2015-12-01

    The experimental identification of the mechanism by which extinctions of predators trigger further predator extinctions emphasizes the role of indirect effects between species in disturbed ecosystems. It also has deep consequences for the hidden magnitude of the current biodiversity crisis.

  15. Extinction Curves of Lensing Galaxies

    Science.gov (United States)

    Elíasdóttir, Árdís

    2006-09-01

    Dust extinction causes light from distant sources to be dimmed on itsway to the observer. In cosmological studies, such as SN Ia studies,it is of great importance that the effects of dust extinction becorrectly accounted for. However, although dust properties, andhence extinction, are expected to vary with redshift, not very muchis known about the extinction properties of high redshift galaxies.This is because the methods traditionally used to study extinctioncurves are only applicable for the most nearby galaxies. Studyinggravitationally lensed quasars is an emerging method of studying thedust extinction of high redshift galaxies. I will present an ESO VLTstudy of 10 such lensing galaxies, with redshifts up to 1. The 10systems display varying amount and type of extinction, with thedoubly imaged quasar B1152+199 showing the greatest extinction with A(V)=2.4 and R_V=2.1 for a Galactic type extinction law.

  16. Mass Extinctions Past and Present.

    Science.gov (United States)

    Allmon, Warren Douglas

    1987-01-01

    Discusses some parallels that seem to exist between mass extinction recognizable in the geologic record and the impending extinction of a significant proportion of the earth's species due largely to tropical deforestation. Describes some recent theories of causal factors and periodicities in mass extinction. (Author/TW)

  17. Yohimbine Impairs Extinction of Cocaine-Conditioned Place Preference in an [alpha] [subscript 2]-Adrenergic Receptor Independent Process

    Science.gov (United States)

    Davis, Adeola R.; Shields, Angela D.; Brigman, Jonathan L.; Norcross, Maxine; McElligott, Zoe A.; Holmes, Andrew; Winder, Danny G.

    2008-01-01

    Extinction, a form of learning that has the ability to reshape learned behavior based on new experiences, has been heavily studied utilizing fear learning paradigms. Mechanisms underlying extinction of positive-valence associations, such as drug self-administration and place preference, are poorly understood yet may have important relevance to…

  18. Histone Modifications around Individual BDNF Gene Promoters in Prefrontal Cortex Are Associated with Extinction of Conditioned Fear

    Science.gov (United States)

    Bredy, Timothy W.; Wu, Hao; Crego, Cortney; Zellhoefer, Jessica; Sun, Yi E.; Barad, Mark

    2007-01-01

    Extinction of conditioned fear is an important model both of inhibitory learning and of behavior therapy for human anxiety disorders. Like other forms of learning, extinction learning is long-lasting and depends on regulated gene expression. Epigenetic mechanisms make an important contribution to persistent changes in gene expression; therefore,…

  19. Stressor controllability modulates fear extinction in humans.

    Science.gov (United States)

    Hartley, Catherine A; Gorun, Alyson; Reddan, Marianne C; Ramirez, Franchesca; Phelps, Elizabeth A

    2014-09-01

    Traumatic events are proposed to play a role in the development of anxiety disorders, however not all individuals exposed to extreme stress experience a pathological increase in fear. Recent studies in animal models suggest that the degree to which one is able to control an aversive experience is a critical factor determining its behavioral consequences. In this study, we examined whether stressor controllability modulates subsequent conditioned fear expression in humans. Participants were randomly assigned to an escapable stressor condition, a yoked inescapable stressor condition, or a control condition involving no stress exposure. One week later, all participants underwent fear conditioning, fear extinction, and a test of extinction retrieval the following day. Participants exposed to inescapable stress showed impaired fear extinction learning and increased fear expression the following day. In contrast, escapable stress improved fear extinction and prevented the spontaneous recovery of fear. Consistent with the bidirectional controllability effects previously reported in animal models, these results suggest that one's degree of control over aversive experiences may be an important factor influencing the development of psychological resilience or vulnerability in humans.

  20. Discreteness induced extinction

    Science.gov (United States)

    dos Santos, Renato Vieira; da Silva, Linaena Méricy

    2015-11-01

    Two simple models based on ecological problems are discussed from the point of view of non-equilibrium statistical mechanics. It is shown how discrepant may be the results of the models that include spatial distribution with discrete interactions when compared with the continuous analogous models. In the continuous case we have, under certain circumstances, the population explosion. When we take into account the finiteness of the population, we get the opposite result, extinction. We will analyze how these results depend on the dimension d of the space and describe the phenomenon of the "Discreteness Inducing Extinction" (DIE). The results are interpreted in the context of the "paradox of sex", an old problem of evolutionary biology.

  1. Contextual-Specificity of Short-Delay Extinction in Humans: Renewal of Fear-Potentiated Startle in a Virtual Environment

    Science.gov (United States)

    Alvarez, Ruben P.; Johnson, Linda; Grillon, Christian

    2007-01-01

    A recent fear-potentiated startle study in rodents suggested that extinction was not context dependent when extinction was conducted after a short delay following acquisition, suggesting that extinction can lead to erasure of fear learning in some circumstances. The main objective of this study was to attempt to replicate these findings in humans…

  2. Extinction cascades partially estimate herbivore losses in a complete Lepidoptera--plant food web.

    Science.gov (United States)

    Pearse, Ian S; Altermatt, Florian

    2013-08-01

    The loss of species from an ecological community can have cascading effects leading to the extinction of other species. Specialist herbivores are highly diverse and may be particularly susceptible to extinction due to host plant loss. We used a bipartite food web of 900 Lepidoptera (butterfly and moth) herbivores and 2403 plant species from Central Europe to simulate the cascading effect of plant extinctions on Lepidoptera extinctions. Realistic extinction sequences of plants, incorporating red-list status, range size, and native status, altered subsequent Lepidoptera extinctions. We compared simulated Lepidoptera extinctions to the number of actual regional Lepidoptera extinctions and found that all predicted scenarios underestimated total observed extinctions but accurately predicted observed extinctions attributed to host loss (n = 8, 14%). Likely, many regional Lepidoptera extinctions occurred for reasons other than loss of host plant alone, such as climate change and habitat loss. Ecological networks can be useful in assessing a component of extinction risk to herbivores based on host loss, but further factors may be equally important.

  3. Humidity Dependent Extinction of Clay Aerosols

    Science.gov (United States)

    Greenslade, M. E.; Attwood, A. R.

    2010-12-01

    Aerosols play an important role in the Earth’s radiative balance by directly scattering and absorbing radiation. The magnitude of aerosol forcing can be altered by changes in relative humidity which cause aerosol size, shape and refractive index to vary. To quantify these effects, a custom cavity ring down instrument operated at 532 nm with two sample channels measures aerosols extinction under dry conditions and at elevated humidity. The optical growth, fRH(ext), is determined as a ratio of the extinction cross section at high relative humidity to that under dry conditions. Three key clay components of mineral dust and mixtures of clay components with ammonium sulfate are investigated using this method. Experimentally obtained optical growth is compared with physical growth factors from the literature and our work determined using several different techniques. Further, Mie theory calculations based on published optical constants are compared with experimental results. Differences between theory and experiment will be discussed.

  4. A theoretical quantitative genetic study of negative ecological interactions and extinction times in changing environments

    OpenAIRE

    Jones Adam G

    2008-01-01

    Abstract Background Rapid human-induced changes in the environment at local, regional and global scales appear to be contributing to population declines and extinctions, resulting in an unprecedented biodiversity crisis. Although in the short term populations can respond ecologically to environmental alterations, in the face of persistent change populations must evolve or become extinct. Existing models of evolution and extinction in changing environments focus only on single species, even th...

  5. The Memory System Engaged During Acquisition Determines the Effectiveness of Different Extinction Protocols.

    Science.gov (United States)

    Goodman, Jarid; Packard, Mark G

    2015-01-01

    Previous research indicates that extinction of rodent maze behavior may occur without explicit performance of the previously acquired response. In latent extinction, confining an animal to a previously rewarded goal location without reinforcement is typically sufficient to produce extinction of maze learning. However, previous studies have not determined whether latent extinction may be successfully employed to extinguish all types of memory acquired in the maze, or whether only specific types of memory may be vulnerable to latent extinction. The present study examined whether latent extinction may be effective across two plus-maze tasks that depend on anatomically distinct neural systems. Adult male Long-Evans rats were trained in a hippocampus-dependent place learning task (Experiment 1), in which animals were trained to approach a consistent spatial location for food reward. A separate group of rats were trained in a dorsolateral striatum-dependent response learning task (Experiment 2), in which animals were trained to make a consistent egocentric body-turn response for food reward. Following training, animals received response extinction or latent extinction. For response extinction, animals were given the opportunity to execute the original running approach response toward the empty food cup. For latent extinction, animals were confined to the original goal locations with the empty food cup, thus preventing them from making the original running approach response. Results indicate that, relative to no extinction, latent extinction was effective at extinguishing memory in the place learning task, but remained ineffective in the response learning task. In contrast, typical response extinction remained very effective at extinguishing memory in both place and response learning tasks. The present findings confirm that extinction of maze learning may occur with or without overt performance of the previously acquired response, but that the effectiveness of latent

  6. THE MEMORY SYSTEM ENGAGED DURING ACQUISITION DETERMINES THE EFFECTIVENESS OF DIFFERENT EXTINCTION PROTOCOLS

    Directory of Open Access Journals (Sweden)

    Jarid eGoodman

    2015-11-01

    Full Text Available Previous research indicates that extinction of rodent maze behavior may occur without explicit performance of the previously required response. In latent extinction, confining an animal to a previously rewarded goal location without reinforcement is typically sufficient to produce extinction of maze learning. However, previous studies have not determined whether latent extinction may be successfully employed to extinguish all types of memory acquired in the maze, or whether only specific types of memory may be vulnerable to latent extinction. The present study examined whether latent extinction may be effective across two plus-maze tasks that depend on anatomically distinct neural systems. Adult male Long-Evans rats were trained in a hippocampus-dependent place learning task (experiment 1, in which animals were trained to approach a consistent spatial location for food reward. A separate group of rats were trained in a dorsolateral striatum-dependent response learning task (experiment 2, in which animals were trained to make a consistent egocentric body-turn response for food reward. Following training, animals received response extinction or latent extinction. For response extinction, animals were given the opportunity to execute the original running approach response toward the empty food cup. For latent extinction, animals were confined to the original goal locations with the empty food cup, thus preventing them from making the original running approach response. Results indicate that, relative to no extinction, latent extinction was effective at extinguishing memory in the place learning task, but remained ineffective in the response learning task. In contrast, typical response extinction remained very effective at extinguishing memory in both place and response learning tasks. The present findings confirm that extinction of maze learning may occur with or without overt performance of the previously acquired response, but that the

  7. Taste-immunosuppression engram: reinforcement and extinction.

    Science.gov (United States)

    Niemi, Maj-Britt; Härting, Margarete; Kou, Wei; Del Rey, Adriana; Besedovsky, Hugo O; Schedlowski, Manfred; Pacheco-López, Gustavo

    2007-08-01

    Several Pavlovian conditioning paradigms have documented the brain's abilities to sense immune-derived signals or immune status, associate them with concurrently relevant extereoceptive stimuli, and reinstate such immune responses on demand. Specifically, the naturalistic relation of food ingestion with its possible immune consequences facilitates taste-immune associations. Here we demonstrate that the saccharin taste can be associated with the immunosuppressive agent cyclosporine A, and that such taste-immune associative learning is subject to reinforcement. Furthermore, once consolidated, this saccharin-immunosuppression engram is resistant to extinction when avoidance behavior is assessed. More importantly, the more this engram is activated, either at association or extinction phases, the more pronounced is the conditioned immunosuppression.

  8. Rescuing Ecosystems from Extinction Cascades

    Science.gov (United States)

    Sahasrabudhe, Sagar; Motter, Adilson

    2010-03-01

    Food web perturbations stemming from climate change, overexploitation, invasive species, and natural disasters often cause an initial loss of species that results in a cascade of secondary extinctions. Using a predictive modeling framework, here we will present a systematic network-based approach to reduce the number of secondary extinctions. We will show that the extinction of one species can often be compensated by the concurrent removal of a second specific species, which is a counter-intuitive effect not previously tested in complex food webs. These compensatory perturbations frequently involve long-range interactions that are not a priori evident from local predator-prey relationships. Strikingly, in numerous cases even the early removal of a species that would eventually be extinct by the cascade is found to significantly reduce the number of cascading extinctions. Other nondestructive interventions based on partial removals and growth suppression and/or mortality increase are shown to sometimes prevent all secondary extinctions.

  9. Extinction Events Can Accelerate Evolution

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate...... evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending...... computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific...

  10. Lead Exposure Impairs Hippocampus Related Learning and Memory by Altering Synaptic Plasticity and Morphology During Juvenile Period.

    Science.gov (United States)

    Wang, Tao; Guan, Rui-Li; Liu, Ming-Chao; Shen, Xue-Feng; Chen, Jing Yuan; Zhao, Ming-Gao; Luo, Wen-Jing

    2016-08-01

    Lead (Pb) is an environmental neurotoxic metal. Pb exposure may cause neurobehavioral changes, such as learning and memory impairment, and adolescence violence among children. Previous animal models have largely focused on the effects of Pb exposure during early development (from gestation to lactation period) on neurobehavior. In this study, we exposed Sprague-Dawley rats during the juvenile stage (from juvenile period to adult period). We investigated the synaptic function and structural changes and the relationship of these changes to neurobehavioral deficits in adult rats. Our results showed that juvenile Pb exposure caused fear-conditioned memory impairment and anxiety-like behavior, but locomotion and pain behavior were indistinguishable from the controls. Electrophysiological studies showed that long-term potentiation induction was affected in Pb-exposed rats, and this was probably due to excitatory synaptic transmission impairment in Pb-exposed rats. We found that NMDA and AMPA receptor-mediated current was inhibited, whereas the GABA synaptic transmission was normal in Pb-exposed rats. NR2A and phosphorylated GluR1 expression decreased. Moreover, morphological studies showed that density of dendritic spines declined by about 20 % in the Pb-treated group. The spine showed an immature form in Pb-exposed rats, as indicated by spine size measurements. However, the length and arborization of dendrites were unchanged. Our results suggested that juvenile Pb exposure in rats is associated with alterations in the glutamate receptor, which caused synaptic functional and morphological changes in hippocampal CA1 pyramidal neurons, thereby leading to behavioral changes. PMID:26141123

  11. Sex differences and estrous cycle in female rats interact with the effects of fluoxetine treatment on fear extinction.

    Science.gov (United States)

    Lebrón-Milad, K; Tsareva, A; Ahmed, N; Milad, M R

    2013-09-15

    A common treatment for anxiety disorders is chronic administration of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine. Recent data suggest that SSRIs modulate fear responses after conditioned fear extinction and that gonadal hormones influence fear extinction. In this study we investigated the influence of sex and the estrous cycle on the effects of acute (experiment 1) and chronic (experiment 2) fluoxetine treatment on fear extinction. In experiment 1, rats received tone-footshock pairings during day 1. On day 2, rats received either fluoxetine (10mg/kg in 0.5mL) or vehicle prior to extinction learning. On day 3, extinction memory was assessed during extinction recall. In experiment 2, rats were exposed to a similar behavioral protocol, except that fluoxetine and vehicle were administered for 14 consecutives days after conditioning (days 2-15). Extinction learning and extinction recall occurred on days 15 and 16, respectively. Acute administration of fluoxetine increased fear responses equally in males and females during extinction learning and extinction recall. Chronic administration of fluoxetine reduced fear responses during extinction learning and extinction recall in female but not in male rats and this effect seems to be modulated by the estrous cycle. The SSRI-induced reduction of freezing during extinction learning and recall suggest a general anxiolytic effect of the drug treatment rather than a specific effect on extinction learning per se. Our data show evidence of sex-specific anxiolytic effects of 14-day treatment of fluoxetine while the acute anxiogenic effect of SSRI seems independent of sex effects. PMID:23886596

  12. High extinction amplitude modulation in ultrashort pulse shaping

    CERN Document Server

    Lin, Yen-Wei

    2016-01-01

    We explored the issues related to the resolution and the modulation extinction when filtering the spectrum of a UV femtosecond laser with a standard ultrashort pulse shaper. We have learned that a higher pulse shaping resolution often requires a larger working beam size or a higher density grating for greater dispersion. However, these approaches also introduce more optical errors and degrade the extinction. In this work, we examined specifics of each component to determine the best configuration of our spectral filtering setup. As a proof-of-concept demonstration, we utilized elements available as standard products and achieved 100 GHz filtering resolution with high extinction at the UV-A wavelength, which is superb in this wavelength range. The high extinction spectral filtering is especially important while modifying a broadband laser for the optical control of molecule's internal state.

  13. Extinction and retrieval+extinction of conditioned fear differentially activate medial prefrontal cortex and amygdala in rats

    Directory of Open Access Journals (Sweden)

    Hongjoo Joanne Lee

    2016-01-01

    Full Text Available Pairing a previously neutral conditioned stimulus (CS; e.g., a tone to an aversive unconditioned stimulus (US; e.g., a footshock leads to associative learning such that the tone alone comes to elicit a conditioned response (e.g., freezing. We have previously shown that an extinction session that occurs within the reconsolidation window (termed retrieval+extinction attenuates fear responding and prevents the return of fear in Pavlovian fear conditioning (Monfils et al., 2009. To date, the mechanisms that explain the different behavioral outcomes between standard extinction and retrieval+extinction remain poorly understood. Here we sought to examine the differential temporal engagement of specific neural systems by these 2 approaches using Arc catFISH (cellular compartment analysis of temporal activity using fluorescence in situ hybridization. Our results demonstrate that extinction and retrieval+extinction lead to differential patterns of expression, suggesting that they engage different networks. These findings provide insight into the neural mechanisms that allow extinction during reconsolidation to prevent the return of fear in rats.

  14. Neurobiological Basis of Failure to Recall Extinction Memory in Posttraumatic Stress Disorder

    Science.gov (United States)

    Milad, Mohammed R.; Pitman, Roger K.; Ellis, Cameron B.; Gold, Andrea L.; Shin, Lisa M; Lasko, Natasha B.; Zeidan, Mohamed A.; Handwerger, Kathryn; Orr, Scott P.; Rauch, Scott L.

    2009-01-01

    Background: A clinical characteristic of posttraumatic stress disorder (PTSD) is persistently elevated fear responses to stimuli associated with the traumatic event. The objective herein is to determine whether extinction of fear responses is impaired in PTSD and whether such impairment is related to dysfunctional activation of brain regions known to be involved in fear extinction, viz., amygdala, hippocampus, ventromedial prefrontal cortex (vmPFC), and dorsal anterior cingulate cortex (dACC). Methods: Sixteen individuals diagnosed with PTSD and 15 trauma-exposed non-PTSD controls (TENCs) underwent a two-day fear conditioning and extinction protocol in a 3T fMRI scanner. Conditioning and extinction training were conducted on day 1. Extinction recall (or extinction memory) test was conducted on day 2 (extinguished conditioned stimuli presented in the absence of shock). Skin conductance response (SCR) was scored throughout the experiment as an index of the conditioned response. Results: SCR data revealed no significant differences between groups during acquisition and extinction of conditioned fear on day 1. On day 2, however, PTSD subjects showed impaired recall of extinction memory. Analysis of fMRI data showed greater amygdala activation in the PTSD group during day 1 extinction learning. During extinction recall, lesser activation in hippocampus and vmPFC, and greater activation in dACC, was observed in the PTSD group. The magnitude of extinction memory across all subjects was correlated with activation of hippocampus and vmPFC during extinction recall testing. Conclusions: These findings support the hypothesis that fear extinction is impaired in PTSD. They further suggest that dysfunctional activation in brain structures that mediate fear extinction learning, and especially its recall, underlie this impairment. PMID:19748076

  15. Postretrieval Extinction in Adolescence Prevents Return of Juvenile Fear

    Science.gov (United States)

    Jones, Carolyn E.; Monfils, Marie-H.

    2016-01-01

    Traumatic experiences early in life can contribute to the development of mood and anxiety disorders that manifest during adolescence and young adulthood. In young rats exposed to acute fear or stress, alterations in neural development can lead to enduring behavioral abnormalities. Here, we used a modified extinction intervention…

  16. Regulation of extinction-related plasticity by opioid receptors in the ventrolateral periaqueductal gray matter

    Directory of Open Access Journals (Sweden)

    Ryan Parsons

    2010-08-01

    Full Text Available Recent work has led to a better understanding of the neural mechanisms underlying the extinction of Pavlovian fear conditioning. Long-term synaptic changes in the medial prefrontal cortex (mPFC are critical for extinction learning, but very little is currently known about how the mPFC and other brain areas interact during extinction. The current study examined the effect of drugs that impair the extinction of fear conditioning on the activation of the extracellular-related kinase/mitogen-activated protein kinase (ERK/MAPK in brain regions that likely participate in the consolidation of extinction learning. Inhibitors of opioid and N-methyl-D-aspartic acid (NMDA receptors were applied to the ventrolateral periaqueductal gray matter (vlPAG and amygdala shortly before extinction training. Results from these experiments show that blocking opioid receptors in the vlPAG prevented the formation of extinction memory, whereas NMDA receptor blockade had no effect. Conversely, blocking NMDA receptors in the amygdala disrupted the formation of fear extinction memory, but opioid receptor blockade in the same brain area did not. Subsequent experiments tested the effect of these drug treatments on the activation of the ERK/MAPK signaling pathway in various brain regions following extinction training. Only opioid receptor blockade in the vlPAG disrupted ERK phosphorylation in the mPFC and amygdala. These data support the idea that opiodergic signaling derived from the vlPAG affects plasticity across the brain circuit responsible for the formation of extinction memory.

  17. Extinction from a rationalist perspective.

    Science.gov (United States)

    Gallistel, C R

    2012-05-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: (1) the failure of partial reinforcement to increase reinforcements to acquisition; (2) the partial reinforcement extinction effect; (3) spontaneous recovery; (4) renewal; (5) reinstatement; (6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. PMID:22391153

  18. The effects of compound stimulus extinction and inhibition of noradrenaline reuptake on the renewal of alcohol seeking

    Science.gov (United States)

    Furlong, T M; Pan, M J; Corbit, L H

    2015-01-01

    Alcohol-related stimuli can trigger relapse of alcohol-seeking behaviors even after extended periods of abstinence. Extinction of such stimuli can reduce their impact on relapse; however, the expression of extinction can be disrupted when testing occurs outside the context where extinction learning took place, an effect termed renewal. Behavioral and pharmacological methods have recently been shown to augment extinction learning; yet, it is not known whether the improved expression of extinction following these treatments remains context-dependent. Here we examined whether two methods, compound–stimulus extinction and treatment with the noradrenaline reuptake inhibitor atomoxetine, would reduce the vulnerability of extinction to a change in context. Following alcohol self-administration, responding was extinguished in a distinct context. After initial extinction, further extinction was given to a target stimulus presented in compound with another alcohol-predictive stimulus intended to augment prediction error (Experiment 1) or after a systemic injection of atomoxetine (1.0 mg kg−1; Experiment 2). A stimulus extinguished as part of a compound elicited less responding than a stimulus receiving equal extinction alone regardless of whether animals were tested in the training or extinction context; however, reliable renewal was not observed in this paradigm. Importantly, atomoxetine enhanced extinction relative to controls even in the presence of a reliable renewal effect. Thus, extinction of alcohol-seeking behavior can be improved by extinguishing multiple alcohol-predictive stimuli or enhancing noradrenaline neurotransmission during extinction training. Importantly, both methods improve extinction even when the context is changed between extinction training and test, and thus could be utilized to enhance the outcome of extinction-based treatments for alcohol-use disorders. PMID:26327688

  19. Fear extinction can be made state-dependent on peripheral epinephrine: role of norepinephrine in the nucleus tractus solitarius.

    Science.gov (United States)

    Rosa, Jessica; Myskiw, Jociane C; Furini, Cristiane R G; Sapiras, Gerson G; Izquierdo, Ivan

    2014-09-01

    We investigate whether the extinction of inhibitory avoidance (IA) learning can be subjected to endogenous state-dependence with systemic injections of epinephrine (E), and whether endogenous norepinephrine (NE) and the nucleus tractus solitarius (NTS)→locus coeruleus→hippocampus/amygdala (HIPP/BLA) pathway participate in this. Rats trained in IA were submitted to two sessions of extinction 24 h apart: In the first, the animals were submitted to a training session of extinction, and in the second they were tested for the retention of extinction. Saline or E were given i.p. immediately after the extinction training (post-extinction training injections) and/or 6 min before the extinction test (pre-extinction test). Post-extinction training E (50 or 100 μg/kg) induced a poor retrieval of extinction in the test session of this task unless an additional E injection (50 μg/kg) was given prior to the extinction test. This suggested state-dependence. Muscimol (0.01 μg/side) microinfused into the NTS prior to the extinction test session blocked E-induced state-dependence. Norepinephrine (NE, 1 μg/side) infused bilaterally into NTS restores the extinction impairment caused by post-extinction training i.p. E. In animals with bilateral NTS blockade induced by muscimol, NE (1 μg/side) given prior to the extinction test into the CA1 region of the dorsal hippocampus or into the basolateral amygdala restored the normal extinction levels that had been impaired by muscimol. These results suggest a role for the NTS→locus coeruleus→HIPP/BLA pathway in the retrieval of extinction, as it has been shown to have in the consolidation of inhibitory avoidance and of object recognition learning.

  20. Extinction in multiple virtual reality contexts diminishes fear reinstatement in humans.

    Science.gov (United States)

    Dunsmoor, Joseph E; Ahs, Fredrik; Zielinski, David J; LaBar, Kevin S

    2014-09-01

    Although conditioned fear can be effectively extinguished by unreinforced exposure to a threat cue, fear responses tend to return when the cue is encountered some time after extinction (spontaneous recovery), in a novel environment (renewal), or following presentation of an aversive stimulus (reinstatement). As extinction represents a context-dependent form of new learning, one possible strategy to circumvent the return of fear is to conduct extinction across several environments. Here, we tested the effectiveness of multiple context extinction in a two-day fear conditioning experiment using 3-D virtual reality technology to create immersive, ecologically-valid context changes. Fear-potentiated startle served as the dependent measure. All three experimental groups initially acquired fear in a single context. A multiple extinction group then underwent extinction in three contexts, while a second group underwent extinction in the acquisition context and a third group underwent extinction in a single different context. All groups returned 24h later to test for return of fear in the extinction context (spontaneous recovery) and a novel context (renewal and reinstatement/test). Extinction in multiple contexts attenuated reinstatement of fear but did not reduce spontaneous recovery. Results from fear renewal were tendential. Our findings suggest that multi-context extinction can reduce fear relapse following an aversive event--an event that often induces return of fear in real-world settings--and provides empirical support for conducting exposure-based clinical treatments across a variety of environments. PMID:24583374

  1. Optimising Extinction of Conditioned Disgust

    NARCIS (Netherlands)

    Bosman, Renske C.; Borg, Charmaine; de Jong, Peter J.

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might

  2. Global extinction in spiral galaxies

    NARCIS (Netherlands)

    Tully, RB; Pierce, MJ; Saunders, W; Verheijen, MAW; Witchalls, PL

    1998-01-01

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces Clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in the B, R, I, and K' bands. Extinction causes systematic scatter in color-magnit

  3. Exploring co-extinction correlates

    DEFF Research Database (Denmark)

    Carpaneto, Giuseppe Maria; Mazziotta, Adriano; Pittino, Riccardo;

    2011-01-01

    Co-extinction is a recurring topic in conservation biology. Quantification of co-extinction has been generally restricted to parasite-host, predator-prey and herbivore-host plant interactions. The loss of detritivorous insects upon the depletion of herbivore mammals has been poorly explored. Here...

  4. Acoustic integrated extinction

    CERN Document Server

    Norris, Andrew N

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross-section as a function of wavelength. Sohl et al. [1] derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency.

  5. Reexposure to the Amnestic Agent Alleviates Cycloheximide-Induced Retrograde Amnesia for Reactivated and Extinction Memories

    Science.gov (United States)

    Briggs, James F.; Olson, Brian P.

    2013-01-01

    We investigated whether reexposure to an amnestic agent would reverse amnesia for extinction of learned fear similar to that of a reactivated memory. When cycloheximide (CHX) was administered immediately after a brief cue-induced memory reactivation (15 sec) and an extended extinction session (12 min) rats showed retrograde amnesia for both…

  6. The Role of the Medial Prefrontal Cortex in Trace Fear Extinction

    Science.gov (United States)

    Kwapis, Janine L.; Jarome, Timothy J.; Helmstetter, Fred J.

    2015-01-01

    The extinction of delay fear conditioning relies on a neural circuit that has received much attention and is relatively well defined. Whether this established circuit also supports the extinction of more complex associations, however, is unclear. Trace fear conditioning is a better model of complex relational learning, yet the circuit that…

  7. Selective and Protracted Effect of Nifedipine on Fear Memory Extinction Correlates with Induced Stress Response

    Science.gov (United States)

    Waltereit, Robert; Mannhardt, Sonke; Nescholta, Sabine; Maser-Gluth, Christiane; Bartsch, Dusan

    2008-01-01

    Memory extinction, defined as a decrease of a conditioned response as a function of a non-reinforced conditioned stimulus presentation, has high biological and clinical relevance. Extinction is not a passive reversing or erasing of the plasticity associated with acquisition, but a novel, active learning process. Nifedipine blocks L-type voltage…

  8. Extinction, Reacquisition, and Rapid Forgetting of Eyeblink Conditioning in Developing Rats

    Science.gov (United States)

    Brown, Kevin L.; Freeman, John H.

    2014-01-01

    Eyeblink conditioning is a well-established model for studying the developmental neurobiology of associative learning and memory. However, age differences in extinction and subsequent reacquisition have yet to be studied using this model. The present study examined extinction and reacquisition of eyeblink conditioning in developing rats. In…

  9. Hubble Tarantula Treasury Project. IV. The extinction law

    CERN Document Server

    De Marchi, Guido; Sabbi, Elena; Lennon, Daniel; Anderson, Jay; van der Marel, Roeland; Cignoni, Michele; Grebel, Eva K; Larsen, Soeren; Zaritsky, Dennis; Zeidler, Peter; Gouliermis, Dimitrios; Aloisi, Alessandra

    2015-01-01

    We report on the study of interstellar extinction across the Tarantula nebula (30 Doradus), in the Large Magellanic Cloud, using observations from the Hubble Tarantula Treasury Project in the 0.3 - 1.6 micron range. The considerable and patchy extinction inside the nebula causes about 3500 red clump stars to be scattered along the reddening vector in the colour-magnitude diagrams, thereby allowing an accurate determination of the reddening slope in all bands. The measured slope of the reddening vector is remarkably steeper in all bands than in the the Galactic diffuse interstellar medium. At optical wavelengths, the larger ratio of total-to-selective extinction, namely Rv = 4.5 +/- 0.2, implies the presence of a grey component in the extinction law, due to a larger fraction of large grains. The extra large grains are most likely ices from supernova ejecta and will significantly alter the extinction properties of the region until they sublimate in 50 - 100 Myr. We discuss the implications of this extinction la...

  10. Hubble Tarantula Treasury Project - IV. The extinction law

    Science.gov (United States)

    De Marchi, Guido; Panagia, Nino; Sabbi, Elena; Lennon, Daniel; Anderson, Jay; van der Marel, Roeland; Cignoni, Michele; Grebel, Eva K.; Larsen, Søren; Zaritsky, Dennis; Zeidler, Peter; Gouliermis, Dimitrios; Aloisi, Alessandra

    2016-02-01

    We report on the study of interstellar extinction across the Tarantula Nebula (30 Doradus), in the Large Magellanic Cloud, using observations from the Hubble Tarantula Treasury Project in the 0.3-1.6 μm range. The considerable and patchy extinction inside the nebula causes about 3500 red clump stars to be scattered along the reddening vector in the colour-magnitude diagrams, thereby allowing an accurate determination of the reddening slope in all bands. The measured slope of the reddening vector is remarkably steeper in all bands than in the the Galactic diffuse interstellar medium. At optical wavelengths, the larger ratio of total-to-selective extinction, namely RV = 4.5 ± 0.2, implies the presence of a grey component in the extinction law, due to a larger fraction of large grains. The extra large grains are most likely ices from supernova ejecta and will significantly alter the extinction properties of the region until they sublimate in 50-100 Myr. We discuss the implications of this extinction law for the Tarantula Nebula and in general for regions of massive star formation in galaxies. Our results suggest that fluxes of strongly star-forming regions are likely to be underestimated by a factor of about 2 in the optical.

  11. Extinction Laws toward Stellar Sources within a Dusty Circimstellar Medium and Implications for Type Ia Supernovae

    CERN Document Server

    Nagao, T; Nozawa, T

    2016-01-01

    Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium, using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains, adopting various dust grain models. We {\\bf confirm} that behaviors of the (effective) extinction laws are highly dependent on the properties of CS grains. Especially, the total-to-selective extinction ratio $R_{V}$, which characterizes the extinction law, can be either increased or decreased, compared to the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the $B$ and $V$ bands. We also find that eithe...

  12. Functional Extinctions of Species in Ecological Networks

    OpenAIRE

    Säterberg, Torbjörn

    2016-01-01

    Current rates of extinctions are estimated to be around 1000 times higher than background rates that would occur without anthropogenic impacts. These extinction rates refer to the traditional view of extinctions, i.e. numerical extinctions. This thesis is about another type of extinctions: functional extinctions. Those occur when the abundance of a species is too small to uphold the species’ ecologically interactive role. I have taken a theoretical approach and used dynamical models to invest...

  13. Infant Contingency/Extinction Performance after Observing Partial Reinforcement

    Science.gov (United States)

    Weir, Catherine; Toland, Cynthia; King, Rose Ann; Martin, Lisa Maas

    2005-01-01

    Social information gathering by infants 6 and 12 months old was examined as a foundation for later social learning that may be uniquely human. Infant performance on a contingency/extinction task was studied following a caregiver demonstration of the contingency on varied reinforcement schedules. Infants who observed caregivers receive any…

  14. The effect of morphine on fear extinction in rats.

    Science.gov (United States)

    Morris, M D; Gebhart, G F

    1978-05-31

    Rats were trained on an appetitive discretetrial discriminated-punishment task in which they learned to suppress responding when an intense flashing light predicting punishment was present and to respond rapidly on trials when the flashing light was absent. Once animals were performing discriminatively, 0.75, 3.0, or 6.0 mg/kg of morphine (base) was administered and a fear extinction session consisting of 60 nonshocked presentations of the flashing light was given. Two saline control groups, one that received fear extinction and one that did not, were also included in the experiment. On the day following fear extinction, all rats were tested in the undrugged state on the discriminated punishment problem, but without shock. The rats receiving 3.0 and 6.0 mg/kg of morphine before the fear extinction session were suppressed by the flashing light more than the saline extinction group or the 0.75 mg/kg morphine treatment group. Moreover, the two higher dose morphine groups were suppressed as readily as the saline group that received no fear extinction. These results are attributed to the antiemotionality effects of morphine. PMID:97707

  15. Issues in the extinction of specific stimulus-outcome associations in Pavlovian conditioning.

    Science.gov (United States)

    Delamater, Andrew R

    2012-05-01

    This paper reviews a variety of studies designed to examine the effects of extinction upon control by specific stimulus-outcome (S-O) associations in Pavlovian conditioning. Studies conducted with rats in a magazine approach conditioning paradigm have shown that control by specific S-O associations is normally unaffected by extinction treatments, although other aspects of conditioned responding seem affected in a more enduring way. However, recent work suggests that extinction can undermine control by such associations if it is administered after the conditioned stimulus is weakly encoded. The results from these studies suggest that it may be important to consider multiple response systems in assessing the impact of extinction. Studies conducted with the flavor preference learning paradigm in rats also show that specific S-O associations can be undermined by procedures that involve presenting a flavor cue in the absence of its associated nutrient. These findings provide no support for the view that flavor preference learning necessarily entails some unique learning process that differs from more conventional processes. As in other situations, some of these effects likely involve a masking process, but the extent to which masking or true associative weakening occurs in extinction more generally is a topic that is not well understood. Finally, we present some data to suggest that extinction also involves conditional "occasion-setting" control by contextual cues. Special procedures are recommended in assessing such learning when the goal is to distinguish this form of learning from other more conventional mechanisms of extinction.

  16. ACTH Prevents Deficits in Fear Extinction Associated with Early Life Seizures

    Directory of Open Access Journals (Sweden)

    Andrew T Massey

    2016-05-01

    Full Text Available Early life seizures are often associated with cognitive and psychiatric comorbidities that are detrimental to quality of life. In a rat model of early life seizures (ELS, we explored long-term cognitive outcomes in adult rats. Using ACTH, an endogeneous HPA-axis hormone given to children with severe epilepsy, we sought to prevent cognitive deficits. Through comparisons with dexamethasone, we sought to dissociate the corticosteroid effects of ACTH from other potential mechanisms of action. We found that while rats with a history of ELS were able to acquire a conditioned fear learning paradigm as well as controls, these rats had significant deficits in their ability to extinguish fearful memories. ACTH treatment did not alter any seizure parameters but nevertheless was able to significantly improve this fear extinction, while dexamethasone treatment during the same period did not. This ACTH effect was specific for fear extinction deficits and not for spatial learning deficits in a water maze. Additionally, ACTH did not alter seizure latency or duration suggesting that cognitive and seizure outcomes may be dissociable. Expression levels of melanocortin receptors, which bind ACTH, were found to be significantly lower in animals that had experienced ELS than in control animals, potentially implicating central melanocortin receptor dysregulation in the effects of ELS and suggesting a mechanism of action for ACTH. Taken together, these data suggest that early treatment with ACTH can have significant long-term consequences for cognition in animals with a history of ELS independently of seizure cessation, and may act in part through a CNS melanocortin receptor pathway.

  17. Extinction reveals that primary sensory cortex predicts reinforcement outcome

    OpenAIRE

    Bieszczad, Kasia M.; Weinberger, Norman M.

    2012-01-01

    Primary sensory cortices are traditionally regarded as stimulus analyzers. However, studies of associative learning-induced plasticity in the primary auditory cortex (A1) indicate involvement in learning, memory and other cognitive processes. For example, the area of representation of a tone becomes larger for stronger auditory memories and the magnitude of area gain is proportional to the degree that a tone becomes behaviorally important. Here, we used extinction to investigate whether “beha...

  18. Learning and memory alterations are associated with hippocampal N-acetylaspartate in a rat model of depression as measured by 1H-MRS.

    Directory of Open Access Journals (Sweden)

    Guangjun Xi

    Full Text Available It is generally accepted that cognitive processes, such as learning and memory, are affected in depression. The present study used a rat model of depression, chronic unpredictable mild stress (CUMS, to determine whether hippocampal volume and neurochemical changes were involved in learning and memory alterations. A further aim was to determine whether these effects could be ameliorated by escitalopram treatment, as assessed with the non-invasive techniques of structural magnetic resonance imaging (MRI and magnetic resonance spectroscopy (MRS. Our results demonstrated that CUMS had a dramatic influence on spatial cognitive performance in the Morris water maze task, and CUMS reduced the concentration of neuronal marker N-acetylaspartate (NAA in the hippocampus. These effects could be significantly reversed by repeated administration of escitalopram. However, neither chronic stress nor escitalopram treatment influenced hippocampal volume. Of note, the learning and memory alterations of the rats were associated with right hippocampal NAA concentration. Our results indicate that in depression, NAA may be a more sensitive measure of cognitive function than hippocampal volume.

  19. Spatial memory extinction: a c-Fos protein mapping study.

    Science.gov (United States)

    Méndez-Couz, M; Conejo, N M; Vallejo, G; Arias, J L

    2014-03-01

    While the neuronal basis of spatial memory consolidation has been thoroughly studied, the substrates mediating the process of extinction remain largely unknown. This study aimed to evaluate the functional contribution of selected brain regions during the extinction of a previously acquired spatial memory task in the Morris water maze. For that purpose, we used adult male Wistar rats trained in a spatial reference memory task. Learning-related changes in c-Fos inmunoreactive cells after training were evaluated in cortical and subcortical regions. Results show that removal of the hidden platform in the water maze induced extinction of the previously reinforced escape behavior after 16 trials, without spontaneous recovery 24h later. Extinction was related with significantly higher numbers of c-Fos positive nuclei in amygdala nuclei and prefrontal cortex. On the other hand, the lateral mammillary bodies showed higher number of c-Fos positive cells than the control group. Therefore, in contrast with the results obtained in studies of classical conditioning, we show the involvement of diencephalic structures mediating this kind of learning. In summary, our findings suggest that medial prefrontal cortex, the amygdala complex and diencephalic structures like the lateral mammillary nuclei are relevant for the extinction of spatial memory. PMID:24315832

  20. Orbitofrontal cortex inactivation impairs between- but not within-session Pavlovian extinction: an associative analysis.

    Science.gov (United States)

    Panayi, Marios C; Killcross, Simon

    2014-02-01

    The orbitofrontal cortex (OFC) is argued to be the neural locus of Pavlovian outcome expectancies. Reinforcement learning theories argue that extinction learning in Pavlovian procedures is caused by the discrepancy between the expected value of the outcome (US) that is elicited by a predictive stimulus (CS), and the lack of experienced US. If the OFC represents Pavlovian outcome expectancies that are necessary for extinction learning, then disrupting OFC function prior to extinction training should impair extinction learning. This was tested. In experiment 1, Long Evans rats received infusions of saline or muscimol targeting the lateral OFC prior to three appetitive Pavlovian extinction sessions. Muscimol infused into the OFC disrupted between-session but not within-session extinction behaviour. This finding was not due to muscimol infusions disrupting the memory consolidation process per se as there was no effect of muscimol infusion when administered immediately post session (experiment 2). These findings support a role for the OFC in representing outcome expectancies that are necessary for learning. A number of ways in which disrupting outcome expectancy information might block learning will be discussed in the context of traditional associative learning theories and the associative structures they depend on.

  1. Mass Extinctions in Earth's History

    Science.gov (United States)

    Ward, P. D.

    2002-12-01

    Mass extinctions are short intervals of elevated species death. Possible causes of Earth's mass extinctions are both external (astronomical) and internal (tectonic and biotic changes from planetary mechanisms). Paleontologists have identified five "major" mass extinctions (>50 die-off in less than a million years) and more than 20 other minor events over the past 550 million years. Earlier major extinction events undoubtedly also occurred, but we have no fossil record; these were probably associated with, for example, the early heavy bombardment that cleared out the solar system, the advent of oxygen in the atmosphere, and various "snowball Earth" events. Mass extinctions are viewed as both destructive (species death ) and constructive, in that they allow evolutionary innovation in the wake of species disappearances. From an astrobiological perspective, mass extinctions must be considered as able both to reduce biodiversity and even potentially end life on any planet. Of the five major mass extinctions identified on Earth, only one (the Cretaceous/Tertiary event 65 million years ago that famously killed off the dinosaurs ) is unambiguously related to the impact of an asteroid or comet ( 10-km diameter). The Permian/Triassic (250 Myr ago) and Triassic/Jurassic (202 Myr ago) events are now the center of debate between those favoring impact and those suggesting large volume flooding by basaltic lavas. The final two events, Ordovician (440 Myr ago) and Devonian (370 Myr ago) have no accepted causal mechanisms.

  2. Enhanced extinction of aversive memories by high-frequency stimulation of the rat infralimbic cortex.

    Directory of Open Access Journals (Sweden)

    Mouna Maroun

    Full Text Available Electrical stimulation of the rodent medial prefrontal cortex (mPFC, including the infralimbic cortex (IL, immediately prior to or during fear extinction training facilitates extinction memory. Here we examined the effects of high-frequency stimulation (HFS of the rat IL either prior to conditioning or following retrieval of the conditioned memory, on extinction of Pavlovian fear and conditioned taste aversion (CTA. IL-HFS applied immediately after fear memory retrieval, but not three hours after retrieval or prior to conditioning, subsequently reduced freezing during fear extinction. Similarly, IL-HFS given immediately, but not three hours after, retrieval of a CTA memory reduced aversion during extinction. These data indicate that HFS of the IL may be an effective method for reducing both learned fear and learned aversion.

  3. Failure of α-MSH to delay extinction of conditioned avoidance behavior in rats with lesions in the parafascicular nuclei of the thalamus

    NARCIS (Netherlands)

    Bohus, B.; Wied, D. de

    1967-01-01

    Bilateral lesions in the thalamic parafascicular area facilitate the rate of extinction of a conditioned avoidance response without affecting avoidance learning. Treatment with long-acting α-MSH during extinction failed to affect the rate of extinction of the avoidance response. Since this peptide d

  4. What Caused the Mass Extinction?

    Science.gov (United States)

    Alvarez, Walter; And Others

    1990-01-01

    Presented are the arguments of two different points of view on the mass extinction of the dinosaurs. Evidence of extraterrestrial impact theory and massive volcanic eruption theory are discussed. (CW)

  5. Evolution et extinctions des ichthyosaures

    OpenAIRE

    Fischer, Valentin

    2015-01-01

    lchthyosaurs are marine reptiles that colonized numerous ecological niches during the Mesozoic. ln addition to their morphology similar to that of fast swimming sharks and teleosts, ichthyosaurs have the particularity to go extinct before the CretaceousPalaeogene boundary, during the Cenomanian (early Late Cretaceous). Although many ichthyosaur-rich localities have been known for a long ti me, the extinction phases that marked the ir history were analysed and quantified in detail only recentl...

  6. Reconsidering the extinction of ichthyosaurs

    OpenAIRE

    Fischer, Valentin

    2010-01-01

    Despite their extreme adaptation to life in open sea, ichthyosaurs were one of the first major groups of post-Triassic marine reptiles to disappear, at the end of Cenomanian, whereas plesiosaurs, mosasaurs and numerous families of marine crocodiles and sea turtles disappeared during the Cretaceous/Paleocene Extinction Event. It has been proposed that unique biological factors drove ichthyosaurs to extinction, namely a break in the food chain at the level of belemnites or a progressive ecologi...

  7. Infectious Disease, Endangerment, and Extinction

    OpenAIRE

    MacPhee, Ross D. E.; Greenwood, Alex D.

    2013-01-01

    Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief s...

  8. Series cell light extinction monitor

    Science.gov (United States)

    Novick, Vincent J.

    1990-01-01

    A method and apparatus for using the light extinction measurements from two or more light cells positioned along a gasflow chamber in which the gas volumetric rate is known to determine particle number concentration and mass concentration of an aerosol independent of extinction coefficient and to determine estimates for particle size and mass concentrations. The invention is independent of particle size. This invention has application to measurements made during a severe nuclear reactor fuel damage test.

  9. The Sixth Great Mass Extinction

    Science.gov (United States)

    Wagler, Ron

    2012-01-01

    Five past great mass extinctions have occurred during Earth's history. Humanity is currently in the midst of a sixth, human-induced great mass extinction of plant and animal life (e.g., Alroy 2008; Jackson 2008; Lewis 2006; McDaniel and Borton 2002; Rockstrom et al. 2009; Rohr et al. 2008; Steffen, Crutzen, and McNeill 2007; Thomas et al. 2004;…

  10. Magnetic reversals and mass extinctions

    Science.gov (United States)

    Raup, D. M.

    1985-01-01

    The results of a study of reversals of the earth's magnetic field over the past 165 Myr are presented. A stationary periodicity of 30 Myr emerges which predicts pulses of increased reversal activity centered at 10, 40, 70, . . . Myr before the present. The correlation between the reversal intensity and biological extinctions is examined, and a nontrivial discrepancy is found between the magnetic and extinction periodicity.

  11. Extinction and the associative structure of heterogeneous instrumental chains.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2016-09-01

    Drug abuse, overeating, and smoking are all examples of instrumental behaviors that often involve chains or sequences of behavior. A behavior chain is minimally composed of a procurement response that is required in order for a subsequent consumption response to be reinforced. Despite the translational importance of behavior chains, few studies have attempted to understand what binds them together and takes them apart. This article surveys the development of the heterogeneous instrumental chain method and introduces recent findings that have used extinction to analyze the associative content of (what is learned in) the chain. Chained responses that are occasion-set by their own discriminative stimuli may be directly associated; extinction of the procurement response weakens its associated consumption response, and extinction of the consumption response weakens its associated procurement response. Extinction itself involves learning to inhibit the response. Extinguished chained responses are subject to renewal when they are tested either back in the acquisition context or in a new context. In addition, a consumption response that is extinguished outside its chain is renewed when returned to the context of the preceding response in the chain. Research on heterogeneous behavior chains can provide important insights into an important but often overlooked aspect of instrumental learning.

  12. Extinction, relapse, and behavioral momentum.

    Science.gov (United States)

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-05-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior.

  13. Extinction, relapse, and behavioral momentum.

    Science.gov (United States)

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-05-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior. PMID:20152889

  14. Increases in Doublecortin Immunoreactivity in the Dentate Gyrus following Extinction of Heroin-Seeking Behavior

    Directory of Open Access Journals (Sweden)

    Megan P. Hicks

    2012-01-01

    Full Text Available Adult-generated neurons in the dentate gyrus (DG of the hippocampus play a role in various forms of learning and memory. However, adult born neurons in the DG, while still at an immature stage, exhibit unique electrophysiological properties and are also functionally implicated in learning and memory processes. We investigated the effects of extinction of drug-seeking behavior on the formation of immature neurons in the DG as assessed by quantification of doublecortin (DCX immunoreactivity. Rats were allowed to self-administer heroin (0.03 mg/kg/infusion for 12 days and then subjected either to 10 days of extinction training or forced abstinence. We also examined extinction responding patterns following heroin self-administration in glial fibrillary acidic protein thymidine kinase (GFAP-tk transgenic mice, which have been previously demonstrated to show reduced formation of immature and mature neurons in the DG following treatment with ganciclovir (GCV. We found that extinction training increased DCX immunoreactivity in the dorsal DG as compared with animals undergoing forced abstinence, and that GCV-treated GFAP-tk mice displayed impaired extinction learning as compared to saline-treated mice. Our results suggest that extinction of drug-seeking behavior increases the formation of immature neurons in the DG and that these neurons may play a functional role in extinction learning.

  15. Task-specific enhancement of hippocampus-dependent learning in mice deficient in monoacylglycerol lipase, the major hydrolyzing enzyme of the endocannabinoid 2-arachidonoylglycerol

    Directory of Open Access Journals (Sweden)

    Yasushi eKishimoto

    2015-06-01

    Full Text Available Growing evidence indicates that the endocannabinoid system is important for the acquisition and/or extinction of learning and memory. However, it is unclear which endocannabinoid(s play(s a crucial role in these cognitive functions, especially memory extinction. To elucidate the physiological role of 2-arachidonoylglycerol (2-AG, a major endocannabinoid, in behavioral and cognitive functions, we conducted a comprehensive behavioral test battery in knockout (KO mice deficient in monoacylglycerol lipase (MGL, the major hydrolyzing enzyme of 2-AG. We found age-dependent increases in spontaneous physical activity in MGL KO mice. Next, we tested the MGL KO mice using 5 hippocampus-dependent learning paradigms (i.e., Morris water maze [MWM], contextual fear conditioning, novel object recognition test, trace eyeblink conditioning, and water-finding test. In the MWM, MGL KO mice showed normal acquisition of reference memory, but exhibited significantly faster extinction of the learned behavior. Moreover, they showed faster memory acquisition on the reversal-learning task of the MWM. In contrast, in the contextual fear conditioning, MGL KO mice tended to show slower memory extinction. In the novel object recognition and water-finding tests, MGL KO mice exhibited enhanced memory acquisition. Trace eyeblink conditioning was not altered in MGL KO mice throughout the acquisition and extinction phases. These results indicate that 2-AG signaling is important for hippocampus-dependent learning and memory, but its contribution is highly task-dependent.

  16. Altered statistical learning and decision-making in methamphetamine dependence: Evidence from a two-armed bandit task

    Directory of Open Access Journals (Sweden)

    Katia M Harlé

    2015-12-01

    Full Text Available Understanding how humans weigh long-term and short-term goals is important for both basic cognitive science and clinical neuroscience, as substance users need to balance the appeal of an immediate high versus the long-term goal of sobriety. We use a computational model to identify learning and decision-making abnormalities in methamphetamine-dependent individuals (MDI, n=16 versus healthy control subjects (HCS, n=16, in a two-armed bandit task.In this task, subjects repeatedly choose between two arms with fixed but unknown reward rates. Each choice not only yields potential immediate reward but also information useful for long-term reward accumulation, thus pitting exploration against exploitation. We formalize the task as comprising a learning component, the updating of estimated reward rates based on ongoing observations, and a decision-making component, the choice among options based on current beliefs and uncertainties about reward rates. We model the learning component as iterative Bayesian inference (the Dynamic Belief Model, and the decision component using five competing decision policies: Win-stay/Lose-shift (WSLS, ε-Greedy, τ-Switch, Softmax, Knowledge Gradient. HCS and MDI significantly differ in how they learn about reward rates and use them to make decisions. HCS learn from past observations but weigh recent data more, and their decision policy is best fit as Softmax. MDI are more likely to follow the simple learning-independent policy of WSLS, and among MDI best fit by Softmax, they have more pessimistic prior beliefs about reward rates and are less likely to choose the option estimated to be most rewarding. Neurally, MDI’s tendency to avoid the most rewarding option is associated with a lower grey matter volume of the thalamic dorsal lateral nucleus. More broadly, our work illustrates the ability of our computational framework to help reveal subtle learning and decision-making abnormalities in substance use.

  17. Do you know the extinction in your young massive cluster?

    CERN Document Server

    De Marchi, Guido; Sabbi, Elena

    2015-01-01

    Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, with considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars, from basic luminosities and effective temperatures to masses and ages, we must understand and measure the local extinction law. This problem affects all the massive young clusters discussed in his volume. We have developed a powerful method to unambiguously determine the extinction law in an uniform way across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC). In the Large Magellanic Cloud, with about 20 RC stars per arcmin^2, we can easily derive a solid and self-consistent absolute extinction curve over the entire wavelength range of the photometry. Here, we present th...

  18. Potential Association of Lead Exposure During Early Development of Mice With Alteration of Hippocampus Nitric Oxide Levels and Learning Memory

    Institute of Scientific and Technical Information of China (English)

    LI SUN; ZHENG-YAN ZHAO; JIAN HU; XIE-LAI ZHOU

    2005-01-01

    Objective Chronic lead (Pb) exposure during development is known to produce learning deficits. Nitric oxide participates in the synaptic mechanisms involved in certain forms of learning and memory. This study was designed to clarify whether Pb-induced impairment in learning and memory was associated with the changes of nitric oxide levels in mice brains.Methods Sixty Balb/c mice aged 10 days were chosen. A model of lead exposure was established by drinking 0.025%, 0.05%,0.075% lead acetate, respectively for 8 weeks. The controls were orally given distilled water. The ability to learn and memorize was examined by open field test, T-water maze test. In parallel with the behavioral data, NO level of hippocampus tissue was detected by biochemical assay. Results Compared with control groups, (1) the weight of 0.075% group was significantly reduced (P<0.05); (2) The number of times in mice attaining the required standards in T-water maze test was lower in 0.075%group (P<0.01). No significant difference was found between experimental and control groups in open field test (P>0.05); (3)NO level of mouse hippocampus tissue was decreased in 0.075% group (P<0.01). Conclusions The findings suggest that decreased hippocampus NO level may contribute to the Pb-induced deficits in learning and memory processes.

  19. Exogenous prenatal corticosterone exposure mimics the effects of prenatal stress on adult brain stress response systems and fear extinction behavior.

    Science.gov (United States)

    Bingham, Brian C; Sheela Rani, C S; Frazer, Alan; Strong, Randy; Morilak, David A

    2013-11-01

    Exposure to early-life stress is a risk factor for the development of cognitive and emotional disorders later in life. We previously demonstrated that prenatal stress (PNS) in rats results in long-term, stable changes in central stress-response systems and impairs the ability to extinguish conditioned fear responding, a component of post-traumatic stress disorder (PTSD). Maternal corticosterone (CORT), released during prenatal stress, is a possible mediator of these effects. The purpose of the present study was to investigate whether fetal exposure to CORT at levels induced by PNS is sufficient to alter the development of adult stress neurobiology and fear extinction behavior. Pregnant dams were subject to either PNS (60 min immobilization/day from ED 14-21) or a daily injection of CORT (10mg/kg), which approximated both fetal and maternal plasma CORT levels elicited during PNS. Control dams were given injections of oil vehicle. Male offspring were allowed to grow to adulthood undisturbed, at which point they were sacrificed and the medial prefrontal cortex (mPFC), hippocampus, hypothalamus, and a section of the rostral pons containing the locus coeruleus (LC) were dissected. PNS and prenatal CORT treatment decreased glucocorticoid receptor protein levels in the mPFC, hippocampus, and hypothalamus when compared to control offspring. Both treatments also decreased tyrosine hydroxylase levels in the LC. Finally, the effect of prenatal CORT exposure on fear extinction behavior was examined following chronic stress. Prenatal CORT impaired both acquisition and recall of cue-conditioned fear extinction. This effect was additive to the impairment induced by previous chronic stress. Thus, these data suggest that fetal exposure to high levels of maternal CORT is responsible for many of the lasting neurobiological consequences of PNS as they relate to the processes underlying extinction of learned fear. The data further suggest that adverse prenatal environments constitute a

  20. Extinction Laws toward Stellar Sources within a Dusty Circumstellar Medium and Implications for Type Ia Supernovae

    Science.gov (United States)

    Nagao, Takashi; Maeda, Keiichi; Nozawa, Takaya

    2016-06-01

    Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate the effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains by adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on the properties of CS grains, especially the total-to-selective extinction ratio R V , which characterizes the extinction law and can be either increased or decreased and compared with the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons are necessary for realizing a low value of R V as often measured toward SNe Ia if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments.

  1. Daily Exposure to Sucrose Impairs Subsequent Learning About Food Cues: A Role for Alterations in Ghrelin Signaling and Dopamine D2 Receptors.

    Science.gov (United States)

    Sharpe, M J; Clemens, K J; Morris, M J; Westbrook, R F

    2016-04-01

    The prevalence of hedonic foods and associated advertising slogans has contributed to the rise of the obesity epidemic in the modern world. Research has shown that intake of these foods disrupt dopaminergic systems. It may be that a disruption of these circuits produces aberrant learning about food-cue relationships. We found that rodents given 28 days of intermittent access to sucrose exhibited a deficit in the ability to block learning about a stimulus when it is paired in compound with food and another stimulus that has already been established as predictive of the food outcome. This deficit was characterized by an approach to a cue signaling food delivery that is usually blocked by prior learning, an effect dependent on dopaminergic prediction-error signaling in the midbrain. Administering the D2 agonist quinpirole during learning restored blocking in animals with a prior history of sucrose exposure. Further, repeated central infusions of ghrelin produced a deficit in blocking in the same manner as sucrose exposure. We argue that changes in dopaminergic systems resulting from sucrose exposure are mediated by a disruption of ghrelin signaling as rodents come to anticipate delivery of the highly palatable sucrose outside of normal feeding schedules. This suggestion is supported by our finding that both sucrose and ghrelin treatments resulted in increases in amphetamine-induced locomotor responding. Thus, for the first time, we have provided evidence of a potential link between alterations in D2 receptors caused by the intake of hedonic foods and aberrant learning about cue-food relationships capable of promoting inappropriate feeding habits. In addition, we have found preliminary evidence to suggest that this is mediated by changes in ghrelin signaling, a finding that should stimulate further research into modulation of ghrelin activity to treat obesity. PMID:26365954

  2. Glucocorticoid receptors and extinction retention deficits in the single prolonged stress model.

    Science.gov (United States)

    Knox, D; Nault, T; Henderson, C; Liberzon, I

    2012-10-25

    Single prolonged stress (SPS) is a rodent model of post traumatic stress disorder that is comprised of serial application of restraint (r), forced swim (fs), and ether (eth) followed by a 7-day quiescent period. SPS induces extinction retention deficits and it is believed that these deficits are caused by the combined stressful effect of serial exposure to r, fs, and eth. However, this hypothesis remains untested. Neurobiological mechanisms by which SPS induces extinction retention deficits are unknown, but SPS enhances glucocorticoid receptor (GR) expression in the hippocampus, which is critical for contextual modulation of extinction retrieval. Upregulation of GRs in extinction circuits may be a mechanism by which SPS induces extinction retention deficits, but this hypothesis has not been examined. In this study, we systematically altered the stressors that constitute SPS (i.e. r, fs, eth), generating a number of partial SPS (p-SPS) groups, and observed the effects SPS and p-SPSs had on extinction retention and GR levels in the hippocampus and prefrontal cortex (PFC). PFC GRs were assayed, because regions of the PFC are critical for maintaining extinction. We predicted that only exposure to full SPS would result in extinction retention deficits and enhance hippocampal and PFC GR levels. Only exposure to full SPS induced extinction retention deficits. Hippocampal and PFC GR expression was enhanced by SPS and most p-SPSs, however hippocampal GR expression was significantly larger following the full SPS exposure than all other conditions. Our findings suggest that the combined stressful effect of serial exposure to r, fs, and eth results in extinction retention deficits. The results also suggest that simple enhancements in GR expression in the hippocampus and PFC are insufficient to result in extinction retention deficits, but raise the possibility that a threshold-enhancement in hippocampal GR expression contributes to SPS-induced extinction retention deficits

  3. Neuro-Linguistic Programming and Altered States: Encouraging Preparation for Learning in the Classroom for Students with Special Educational Needs

    Science.gov (United States)

    Kudliskis, Voldis

    2013-01-01

    In seeking to identify the processes associated with the immediate engagement of learning for students with mild special educational needs, this study examined the responses of an extraction group (n = 7) of 11- to 13-year-old students who participated in a number of lessons in which the opening episode involved the use of visualisation techniques…

  4. Continuous theta-burst stimulation (cTBS) over the lateral prefrontal cortex alters reinforcement learning bias

    NARCIS (Netherlands)

    Ott, D.V.M.; Ullsperger, M.; Jocham, G.; Neumann, J.; Klein, T.A.

    2011-01-01

    The prefrontal cortex is known to play a key role in higher-order cognitive functions. Recently, we showed that this brain region is active in reinforcement learning, during which subjects constantly have to integrate trial outcomes in order to optimize performance. To further elucidate the role of

  5. Continuous theta-burst stimulation (cTBS) over the lateral prefrontal cortex alters reinforcement learning bias.

    Science.gov (United States)

    Ott, Derek V M; Ullsperger, Markus; Jocham, Gerhard; Neumann, Jane; Klein, Tilmann A

    2011-07-15

    The prefrontal cortex is known to play a key role in higher-order cognitive functions. Recently, we showed that this brain region is active in reinforcement learning, during which subjects constantly have to integrate trial outcomes in order to optimize performance. To further elucidate the role of the dorsolateral prefrontal cortex (DLPFC) in reinforcement learning, we applied continuous theta-burst stimulation (cTBS) either to the left or right DLPFC, or to the vertex as a control region, respectively, prior to the performance of a probabilistic learning task in an fMRI environment. While there was no influence of cTBS on learning performance per se, we observed a stimulation-dependent modulation of reward vs. punishment sensitivity: Left-hemispherical DLPFC stimulation led to a more reward-guided performance, while right-hemispherical cTBS induced a more avoidance-guided behavior. FMRI results showed enhanced prediction error coding in the ventral striatum in subjects stimulated over the left as compared to the right DLPFC. Both behavioral and imaging results are in line with recent findings that left, but not right-hemispherical stimulation can trigger a release of dopamine in the ventral striatum, which has been suggested to increase the relative impact of rewards rather than punishment on behavior. PMID:21554966

  6. Effects of endocannabinoid and endovanilloid systems on aversive memory extinction.

    Science.gov (United States)

    Laricchiuta, Daniela; Centonze, Diego; Petrosini, Laura

    2013-11-01

    In contextual fear conditioning animals have to integrate various elemental stimuli into a coherent representation of the condition and then associate context representation with punishment. Although several studies indicated the modulating role of endocannabinoid system (ECS) on the associative learning, ECS effect on contextual fear conditioning requires further investigations. The present study assessed the effects of the increased endocannabinoid anandamide (AEA) tone on acquisition, retrieval and extinction of the contextual fear conditioning. Given that AEA may bind to cannabinoid type 1 (CB1) receptors as well as to postsynaptic ionotropic Transient Receptor Potential Vanilloid type 1 (TRPV1) channels, particular attention was paid in determining how the increased AEA tone influenced fear responses. Furthermore, it was investigated how the ECS modulated the effects of stress-sensitization on fear response. Thus, mice submitted or not to a social defeat stress protocol were treated with drugs acting on ECS, CB1 receptors or TRPV1 channels and tested in a contextual fear conditioning whose conditioning, retrieval and extinction phases were analyzed. ECS activation influenced the extinction process and contrasted the stress effects on fear memory. Furthermore, CB1 receptor antagonist blocked and TRPV1 channel antagonist promoted short- and long-term extinction. The present study indicates that ECS controls the extinction of aversive memories in the contextual fear conditioning. PMID:23948212

  7. Measuring Galactic Extinction A Test

    CERN Document Server

    Arce, H G; Arce, Hector G.; Goodman, Alyssa A.

    1999-01-01

    We test the recently published all-sky reddening map of Schlegel, Finkbeiner & Davis (1998 [SFD]) using the extinction study of a region in the Taurus dark cloud complex by Arce & Goodman (1999 [AG]). In their study, AG use four different techniques to measure the amount and structure of the extinction toward Taurus, and all four techniques agree very well. Thus we believe that the AG results are a truthful representation of the extinction in the region and can be used to test the reliability of the SFD reddening map. The results of our test show that the SFD all-sky reddening map, which is based on data from COBE/DIRBE and IRAS/ISSA, overestimates the reddening by a factor of 1.3 to 1.5 in regions of smooth extinction with A_V > 0.5 mag. In some regions of steep extinction gradients the SFD map underestimates the reddening value, probably due to its low spatial resolution. We expect that the astronomical community will be using the SFD reddening map extensively. We offer this Letter as a cautionary n...

  8. The effects of transcutaneous vagus nerve stimulation on conditioned fear extinction in humans.

    Science.gov (United States)

    Burger, Andreas M; Verkuil, Bart; Van Diest, Ilse; Van der Does, Willem; Thayer, Julian F; Brosschot, Jos F

    2016-07-01

    A critical component of the treatment for anxiety disorders is the extinction of fear via repeated exposure to the feared stimulus. This process is strongly dependent on successful memory formation and consolidation. Stimulation of the vagus nerve enhances memory formation in both animals and humans. The objective of this study was to assess whether transcutaneous stimulation of the vagus nerve (tVNS) can accelerate extinction memory formation and retention in fear conditioned humans. To assess fear conditioning and subsequent fear extinction, we assessed US expectancy ratings, fear potentiated startle responses and phasic heart rate responses. We conducted a randomized controlled trial in thirty-one healthy participants. After fear conditioning participants were randomly assigned to receive tVNS or sham stimulation during the extinction phase. Retention of extinction memory was tested 24h later. tVNS accelerated explicit fear extinction learning (US expectancy ratings), but did not lead to better retention of extinction memory 24h later. We did not find a differential physiological conditioning response during the acquisition of fear and thus were unable to assess potential effects of tVNS on the extinction of physiological indices of fear. These findings complement recent studies that suggest vagus nerve stimulation could be a promising tool to improve memory consolidation and fear extinction. PMID:27222436

  9. Differential participation of temporal structures in the consolidation and reconsolidation of taste aversion extinction.

    Science.gov (United States)

    Garcia-Delatorre, Paola; Rodríguez-Ortiz, Carlos J; Balderas, Israela; Bermúdez-Rattoni, Federico

    2010-09-01

    The extinction process has been described as the decline in the frequency or intensity of the conditioned response following the withdrawal of reinforcement. Hence, experimental extinction does not reflect loss of the original memory, but rather reflects new learning, which in turn requires consolidation in order to be maintained in the long term. During extinction of conditioned taste aversion (CTA), a taste previously associated with aversive consequences acquires a safe status through continuous presentations of the flavor with no aversive consequence. In addition, reconsolidation has been defined as the labile state of a consolidated memory after its reactivation by the presentation of relevant information. In this study, we analyzed structures from the temporal lobe that could be involved in consolidation and reconsolidation of extinction of CTA by means of new protein synthesis. Our results showed that protein synthesis in the hippocampus (HC), the perirhinal cortex (PR) and the insular cortex (IC) of rats participate in extinction consolidation, whereas the basolateral amygdala plays no part in this phenomenon. Furthermore, we found that inhibition of protein synthesis in the IC in a third extinction trial had an effect on reconsolidation of extinction. The participation of the HC in taste memory has been described as a downmodulator for CTA consolidation, and has been related to a context-taste association. Altogether, these data suggest that extinction of aversive taste memories are subserved by the IC, HC and PR, and that extinction can undergo reconsolidation, a process depending only on the IC.

  10. Drivers of extinction risk in African mammals: the interplay of distribution state, human pressure, conservation response and species biology

    OpenAIRE

    Di Marco, Moreno; BUCHANAN Graeme, M.; SZANTOI ZOLTAN; Holmgren, Milena; Grottolo Marasini, Gabriele; GROSS DORIT; Tranquilli, Sandra; Boitani, Luigi; Rondinini, Carlo

    2014-01-01

    Although conservation intervention has reversed the decline of some species, our success is outweighed by a much larger number of species moving towards extinction. Extinction risk modelling can identify correlates of risk and species not yet recognized to be threatened. Here, we use machine learning models to identify correlates of extinction risk in African terrestrial mammals using a set of variables belonging to four classes: species distribution state, human pressures, ...

  11. Compound Stimulus Presentation and the Norepinephrine Reuptake Inhibitor Atomoxetine Enhance Long-Term Extinction of Cocaine-Seeking Behavior

    OpenAIRE

    Janak, Patricia H.; Bowers, M. Scott; Corbit, Laura H

    2011-01-01

    Drug abstinence is frequently compromised when addicted individuals are re-exposed to environmental stimuli previously associated with drug use. Research with human addicts and in animal models has demonstrated that extinction learning (non-reinforced cue-exposure) can reduce the capacity of such stimuli to induce relapse, yet extinction therapies have limited long-term success under real-world conditions (Bouton, 2002; O'Brien, 2008). We hypothesized that enhancing extinction would reduce th...

  12. Disturbance-mediated colonization-extinction dynamics in experimental protist metacommunities.

    Science.gov (United States)

    Fukumori, Kayoko; Livingston, George; Leibold, Mathew A

    2015-12-01

    Colonization-extinction dynamics and species sorting among habitats deter- mine the distribution of species within metacommunities. Theory suggests that disturbances reduce the importance of species sorting and enhance spatial patterning and stochastic effects, however this has not yet been experimentally shown. We examined how extinctions in a heterogeneous landscape of patches affects the influence of environmental, spatial, and stochastic factors on community composition in a simple two-species, two-habitat, protist metacommunity where each species dominates in a different habitat type. We imposed four different levels of random extinctions on local patches and monitored changes in the metacommunity through time. We found that near-steady state patterns of community variability developed relatively rapidly (within nine colonization-extinction cycles) and that increased extinction rate produced altered patterns of community regulation by reducing environmental control and increasing spatial and stochastic effects. Our results indicate a possible explanation for the combination of environmental, spatial and stochastic effects observed in natural metacommunities.

  13. The atmospheric extinction of light

    CERN Document Server

    Hughes, Stephen W; Powell, Sean; Carroll, Joshua

    2015-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm^-1 respectively and 0.032, 0.037 and 0.092 cm^-1 for the Picotech Dr. DAQ ADC.

  14. The atmospheric extinction of light

    Science.gov (United States)

    Hughes, Stephen W.; Cowley, Michael; Powell, Sean; Carroll, Joshua

    2016-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm-1 respectively and 0.032, 0.037 and 0.092 cm-1 for the Picotech Dr. DAQ ADC.

  15. Mass extinctions and supernova explosions

    CERN Document Server

    Korschinek, Gunther

    2016-01-01

    A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, or the direct exposure of lethal x-rays. Another indirect effect is cloud formation, induced by cosmic rays in the atmosphere which result in a drop in the Earth's temperature, causing major glaciations of the Earth. The discovery of highly intensive gamma ray bursts (GRBs), which could be connected to SNe, initiated further discussions on possible life-threatening events in Earth's history. The probability that GRBs hit the Earth is very low. Nevertheless, a past interaction of Earth with GRBs and/or SNe cannot be exclude...

  16. Infectious Disease, Endangerment, and Extinction

    Directory of Open Access Journals (Sweden)

    Ross D. E. MacPhee

    2013-01-01

    Full Text Available Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters.

  17. Altered brain activation in a reversal learning task unmasks adaptive changes in cognitive control in writer's cramp

    Directory of Open Access Journals (Sweden)

    Kirsten E. Zeuner

    2016-01-01

    The Brodmann area 32 (BA32 is part of the dorsal anterior cingulate cortex (dACC that plays an important role in coordinating and integrating information to guide behavior and in reward-based learning. The dACC is connected with the basal ganglia-thalamo-loop modulated by dopaminergic signaling. This finding suggests disturbed integration of reinforcement history in decision making and implicate that the reward system might contribute to the pathogenesis in writer's cramp.

  18. The galactic cycle of extinction

    Science.gov (United States)

    Gillman, Michael; Erenler, Hilary

    2008-01-01

    Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

  19. Bidirectional synaptic plasticity in intercalated amygdala neurons and the extinction of conditioned fear responses.

    Science.gov (United States)

    Royer, S; Paré, D

    2002-01-01

    Classical fear conditioning is believed to result from potentiation of conditioned synaptic inputs in the basolateral amygdala. That is, the conditioned stimulus would excite more neurons in the central nucleus and, via their projections to the brainstem and hypothalamus, evoke fear responses. However, much data suggests that extinction of fear responses does not depend on the reversal of these changes but on a parallel NMDA-dependent learning that competes with the first one. Because they control impulse traffic from the basolateral amygdala to the central nucleus, GABAergic neurons of the intercalated cell masses are ideally located to implement this second learning. Consistent with this hypothesis, the present study shows that low- and high-frequency stimulation of basolateral afferents respectively induce long-term depression (LTD) and potentiation (LTP) of responses in intercalated cells. Moreover, induction of LTP and LTD is prevented by application of an NMDA antagonist. To determine how these activity-dependent changes are expressed, we tested whether LTD and LTP induction are associated with modifications in paired-pulse facilitation, an index of transmitter release probability. Only LTP induction was associated with a change in paired-pulse facilitation. Depotentiation of previously potentiated synapses did not revert the modification in paired pulse facilitation, suggesting that LTP is associated with presynaptic alterations, but that LTD and depotentiation depend on postsynaptic changes. Taken together, our results suggest that basolateral synapses onto intercalated neurons can express NMDA-dependent LTP and LTD, consistent with the possibility that intercalated neurons are a critical locus of plasticity for the extinction of conditioned fear responses. Ultimately, these plastic events may prevent conditioned amygdala responses from exciting neurons of the central nucleus, and thus from evoking conditioned fear responses.

  20. D-Cycloserine Does Not Facilitate Fear Extinction by Reducing Conditioned Stimulus Processing or Promoting Conditioned Inhibition to Contextual Cues

    Science.gov (United States)

    Baker, Kathryn D.; McNally, Gavan P.; Richardson, Rick

    2012-01-01

    The NMDA receptor partial agonist d-cycloserine (DCS) enhances the extinction of learned fear in rats and exposure therapy in humans with anxiety disorders. Despite these benefits, little is known about the mechanisms by which DCS promotes the loss of fear. The present study examined whether DCS augments extinction retention (1) through reductions…

  1. Alien plant invasions and native plant extinctions: a six-threshold framework.

    Science.gov (United States)

    Downey, Paul O; Richardson, David M

    2016-01-01

    Biological invasions are widely acknowledged as a major threat to global biodiversity. Species from all major taxonomic groups have become invasive. The range of impacts of invasive taxa and the overall magnitude of the threat is increasing. Plants comprise the biggest and best-studied group of invasive species. There is a growing debate; however, regarding the nature of the alien plant threat-in particular whether the outcome is likely to be the widespread extinction of native plant species. The debate has raised questions on whether the threat posed by invasive plants to native plants has been overstated. We provide a conceptual framework to guide discussion on this topic, in which the threat posed by invasive plants is considered in the context of a progression from no impact through to extinction. We define six thresholds along the 'extinction trajectory', global extinction being the final threshold. Although there are no documented examples of either 'in the wild' (Threshold 5) or global extinctions (Threshold 6) of native plants that are attributable solely to plant invasions, there is evidence that native plants have crossed or breached other thresholds along the extinction trajectory due to the impacts associated with plant invasions. Several factors may be masking where native species are on the trajectory; these include a lack of appropriate data to accurately map the position of species on the trajectory, the timeframe required to definitively state that extinctions have occurred and management interventions. Such interventions, focussing mainly on Thresholds 1-3 (a declining population through to the local extinction of a population), are likely to alter the extinction trajectory of some species. The critical issue for conservation managers is the trend, because interventions must be implemented before extinctions occur. Thus the lack of evidence for extinctions attributable to plant invasions does not mean we should disregard the broader threat. PMID

  2. A theoretical quantitative genetic study of negative ecological interactions and extinction times in changing environments

    Directory of Open Access Journals (Sweden)

    Jones Adam G

    2008-04-01

    Full Text Available Abstract Background Rapid human-induced changes in the environment at local, regional and global scales appear to be contributing to population declines and extinctions, resulting in an unprecedented biodiversity crisis. Although in the short term populations can respond ecologically to environmental alterations, in the face of persistent change populations must evolve or become extinct. Existing models of evolution and extinction in changing environments focus only on single species, even though the dynamics of extinction almost certainly depend upon the nature of species interactions. Results Here, I use a model of quantitative trait evolution in a two-species community to show that negative ecological interactions, such as predation and competition, can produce unexpected results regarding time to extinction. Under some circumstances, negative interactions can be expected to hasten the extinction of species declining in numbers. However, under other circumstances, negative interactions can actually increase times to extinction. This effect occurs across a wide range of parameter values and can be substantial, in some cases allowing a population to persist for 40 percent longer than it would in the absence of the species interaction. Conclusion This theoretical study indicates that negative species interactions can have unexpected positive effects on times to extinction. Consequently, detailed studies of selection and demographics will be necessary to predict the consequences of species interactions in changing environments for any particular ecological community.

  3. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, K.A.; Borges, Paulo A. V.; Ladle, R.J.;

    2010-01-01

    the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...

  4. Modeling Population Growth and Extinction

    Science.gov (United States)

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  5. A model of mass extinction

    CERN Document Server

    Newman, M E J

    1997-01-01

    A number of authors have in recent years proposed that the processes of macroevolution may give rise to self-organized critical phenomena which could have a significant effect on the dynamics of ecosystems. In particular it has been suggested that mass extinction may arise through a purely biotic mechanism as the result of so-called coevolutionary avalanches. In this paper we first explore the empirical evidence which has been put forward in favor of this conclusion. The data center principally around the existence of power-law functional forms in the distribution of the sizes of extinction events and other quantities. We then propose a new mathematical model of mass extinction which does not rely on coevolutionary effects and in which extinction is caused entirely by the action of environmental stresses on species. In combination with a simple model of species adaptation we show that this process can account for all the observed data without the need to invoke coevolution and critical processes. The model al...

  6. Cannabinoid facilitation of fear extinction memory recall in humans

    OpenAIRE

    Rabinak, Christine A.; Angstadt, Mike; Sripada, Chandra S.; James L. Abelson; Liberzon, Israel; Milad, Mohammed R; Phan, K. Luan

    2012-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of th...

  7. D-cycloserine and the facilitation of extinction of conditioned fear: consequences for reinstatement.

    Science.gov (United States)

    Ledgerwood, Lana; Richardson, Rick; Cranney, Jacquelyn

    2004-06-01

    Several recent studies have reported that D-cycloserine (DCS), a partial N-methyl-D-aspartate agonist, facilitates extinction of learned fear in rats. Other studies have shown that representation of the unconditioned stimulus (US) can reinstate learned fear after extinction. This study examined whether this reinstatement effect occurs in Sprague-Dawley rats given DCS at the time of extinction. Results showed that saline-treated rats exhibited the reinstatement effect but DCS-treated rats did not (Experiments 1 and 2). This lack of reinstatement in DCS-treated rats was not due to residual effects of DCS on either US or context processing (Experiment 3). Overall, these results (a) raise questions about the mechanisms underlying DCS facilitation of extinction and (b) suggest that DCS might have substantial practical benefit.

  8. Converging towards the optimal path to extinction

    OpenAIRE

    Schwartz, Ira B.; Forgoston, Eric; Bianco, Simone; Shaw, Leah B.

    2011-01-01

    Extinction appears ubiquitously in many fields, including chemical reactions, population biology, evolution, and epidemiology. Even though extinction as a random process is a rare event, its occurrence is observed in large finite populations. Extinction occurs when fluctuations due to random transitions act as an effective force which drives one or more components or species to vanish. Although there are many random paths to an extinct state, there is an optimal path that maximizes the probab...

  9. Uncertainty-Dependent Extinction of Fear Memory in an Amygdala-mPFC Neural Circuit Model.

    Science.gov (United States)

    Li, Yuzhe; Nakae, Ken; Ishii, Shin; Naoki, Honda

    2016-09-01

    Uncertainty of fear conditioning is crucial for the acquisition and extinction of fear memory. Fear memory acquired through partial pairings of a conditioned stimulus (CS) and an unconditioned stimulus (US) is more resistant to extinction than that acquired through full pairings; this effect is known as the partial reinforcement extinction effect (PREE). Although the PREE has been explained by psychological theories, the neural mechanisms underlying the PREE remain largely unclear. Here, we developed a neural circuit model based on three distinct types of neurons (fear, persistent and extinction neurons) in the amygdala and medial prefrontal cortex (mPFC). In the model, the fear, persistent and extinction neurons encode predictions of net severity, of unconditioned stimulus (US) intensity, and of net safety, respectively. Our simulation successfully reproduces the PREE. We revealed that unpredictability of the US during extinction was represented by the combined responses of the three types of neurons, which are critical for the PREE. In addition, we extended the model to include amygdala subregions and the mPFC to address a recent finding that the ventral mPFC (vmPFC) is required for consolidating extinction memory but not for memory retrieval. Furthermore, model simulations led us to propose a novel procedure to enhance extinction learning through re-conditioning with a stronger US; strengthened fear memory up-regulates the extinction neuron, which, in turn, further inhibits the fear neuron during re-extinction. Thus, our models increased the understanding of the functional roles of the amygdala and vmPFC in the processing of uncertainty in fear conditioning and extinction. PMID:27617747

  10. Uncertainty-Dependent Extinction of Fear Memory in an Amygdala-mPFC Neural Circuit Model

    Science.gov (United States)

    Li, Yuzhe; Nakae, Ken; Ishii, Shin; Naoki, Honda

    2016-01-01

    Uncertainty of fear conditioning is crucial for the acquisition and extinction of fear memory. Fear memory acquired through partial pairings of a conditioned stimulus (CS) and an unconditioned stimulus (US) is more resistant to extinction than that acquired through full pairings; this effect is known as the partial reinforcement extinction effect (PREE). Although the PREE has been explained by psychological theories, the neural mechanisms underlying the PREE remain largely unclear. Here, we developed a neural circuit model based on three distinct types of neurons (fear, persistent and extinction neurons) in the amygdala and medial prefrontal cortex (mPFC). In the model, the fear, persistent and extinction neurons encode predictions of net severity, of unconditioned stimulus (US) intensity, and of net safety, respectively. Our simulation successfully reproduces the PREE. We revealed that unpredictability of the US during extinction was represented by the combined responses of the three types of neurons, which are critical for the PREE. In addition, we extended the model to include amygdala subregions and the mPFC to address a recent finding that the ventral mPFC (vmPFC) is required for consolidating extinction memory but not for memory retrieval. Furthermore, model simulations led us to propose a novel procedure to enhance extinction learning through re-conditioning with a stronger US; strengthened fear memory up-regulates the extinction neuron, which, in turn, further inhibits the fear neuron during re-extinction. Thus, our models increased the understanding of the functional roles of the amygdala and vmPFC in the processing of uncertainty in fear conditioning and extinction. PMID:27617747

  11. From lab to clinic: Extinction of cued cravings to reduce overeating.

    Science.gov (United States)

    Jansen, Anita; Schyns, Ghislaine; Bongers, Peggy; van den Akker, Karolien

    2016-08-01

    Food cue reactivity is a strong motivation to eat, even in the absence of hunger. Therefore, food cue reactivity might sabotage healthy eating, induce weight gain and impede weight loss or weight maintenance. Food cue reactivity can be learned via Pavlovian appetitive conditioning: It is easily acquired but the extinction of appetitive responding seems to be more challenging. Several properties of extinction make it fragile: extinction does not erase the original learning and extinction is context-dependent. These properties threaten full extinction and increase the risk of full relapse. Extinction procedures are discussed to reduce or prevent the occurrence of rapid reacquisition, spontaneous recovery, renewal and reinstatement after extinction. A translation to food cue exposure treatment is made and suggestions are provided, such as conducting the exposure in relevant contexts, using occasional reinforcement and targeting expectancy violation instead of habituation. A new hypothesis proposed here is that the adding of inhibition training to strengthen inhibition skills that reduce instrumental responding, might be beneficial to improve food cue exposure effects. PMID:26994737

  12. Further Evidence of Auditory Extinction in Aphasia

    Science.gov (United States)

    Marshall, Rebecca Shisler; Basilakos, Alexandra; Love-Myers, Kim

    2013-01-01

    Purpose: Preliminary research ( Shisler, 2005) suggests that auditory extinction in individuals with aphasia (IWA) may be connected to binding and attention. In this study, the authors expanded on previous findings on auditory extinction to determine the source of extinction deficits in IWA. Method: Seventeen IWA (M[subscript age] = 53.19 years)…

  13. Determining Extinction Ratio Of A Laser Diode

    Science.gov (United States)

    Unger, Glenn L.

    1992-01-01

    Improved technique to determine extinction ratio of pulsed laser diode based partly on definition of extinction ratio applicable to nonideal laser pulses. Heretofore, determinations involved assumption of ideal laser pulses, and neglected optical power from background light. Because power fluctuates during real pulse, more realistic to define extinction ratio in terms of energy obtained.

  14. Fear conditioning and extinction across development: evidence from human studies and animal models.

    Science.gov (United States)

    Shechner, Tomer; Hong, Melanie; Britton, Jennifer C; Pine, Daniel S; Fox, Nathan A

    2014-07-01

    The ability to differentiate danger and safety through associative processes emerges early in life. Understanding the mechanisms underlying associative learning of threat and safety can clarify the processes that shape development of normative fears and pathological anxiety. Considerable research has used fear conditioning and extinction paradigms to delineate underlying mechanisms in animals and human adults; however, little is known about these mechanisms in children and adolescents. The current paper summarizes the empirical data on the development of fear conditioning and extinction. It reviews methodological considerations and future directions for research on fear conditioning and extinction in pediatric populations. PMID:24746848

  15. Fear conditioning and extinction across development: evidence from human studies and animal models.

    Science.gov (United States)

    Shechner, Tomer; Hong, Melanie; Britton, Jennifer C; Pine, Daniel S; Fox, Nathan A

    2014-07-01

    The ability to differentiate danger and safety through associative processes emerges early in life. Understanding the mechanisms underlying associative learning of threat and safety can clarify the processes that shape development of normative fears and pathological anxiety. Considerable research has used fear conditioning and extinction paradigms to delineate underlying mechanisms in animals and human adults; however, little is known about these mechanisms in children and adolescents. The current paper summarizes the empirical data on the development of fear conditioning and extinction. It reviews methodological considerations and future directions for research on fear conditioning and extinction in pediatric populations.

  16. Extinction-based Processes for Enhancing the Effectiveness of Exposure Therapy

    OpenAIRE

    Culver, Najwa

    2013-01-01

    The dissertation is a three-paper investigation of potential methods for improving exposure therapy outcomes for anxiety disorders. If proven effective, these methods can be utilized to modify exposure therapy for anxiety disorders in order to enhance treatment effects and reduce relapse rates. Study 1 tested a prediction of the Rescorla-Wagner model: that presenting two fear-provoking stimuli simultaneously (compound extinction) would maximize learning during extinction. Participants w...

  17. Effects of recent environmental change on accuracy of inferences of extinction status.

    Science.gov (United States)

    Clements, Christopher F; Collen, Ben; Blackburn, Tim M; Petchey, Owen L

    2014-08-01

    Correctly classifying a species as extinct or extant is of critical importance if current rates of biodiversity loss are to be accurately quantified. Observing an extinction event is rare, so in many cases extinction status is inferred using methods based on the analysis of records of historic sighting events. The accuracy of such methods is difficult to test. However, results of recent experiments with microcosm communities suggest that the rate at which a population declines to extinction, potentially driven by varying environmental conditions, may alter one's ability accurately to infer extinction status. We tested how the rate of population decline, driven by historic environmental change, alters the accuracy of 6 commonly applied sighting-based methods used to infer extinction. We used data from small-scale experimental communities and recorded wild population extirpations. We assessed how accuracy of the different methods was affected by rate of population decline, search effort, and number of sighting events recorded. Rate of population decline and historic population size of the species affected the accuracy of inferred extinction dates; however, faster declines produced more accurate inferred dates of extinction, but only when population sizes were higher. Optimal linear estimation (OLE) offered the most reliable and robust estimates, though no single method performed best in all situations, and it may be appropriate to use a different method if information regarding historic search efforts is available. OLE provided the most accurate estimates of extinction when the number of sighting events used was >10, and future use of this method should take this into account. Data from experimental populations provide added insight into testing techniques to discern wild extirpation events. Care should be taken designing such experiments so that they mirror closely the abundance dynamics of populations affected by real-world extirpation events.

  18. Timing of Extinction Relative to Acquisition: A Parametric Analysis of Fear Extinction in Humans

    OpenAIRE

    Norrholm, Seth D.; Vervliet, Bram; Jovanovic, Tanja; Boshoven, William; Myers, Karyn M.; Davis, Michael; Rothbaum, Barbara; Duncan, Erica J.

    2008-01-01

    Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occurs within minutes of acquisition. However, a limited number of human extinction studies have shown that short interval extinction does not prevent the return of fear. For this reason, we performed ...

  19. Systemic or intrahippocampal delivery of histone deacetylase inhibitors facilitates fear extinction.

    Science.gov (United States)

    Lattal, K Matthew; Barrett, Ruth M; Wood, Marcelo A

    2007-10-01

    Several recent studies have shown that chromatin, the DNA-protein complex that packages genomic DNA, has an important function in learning and memory. Dynamic chromatin modification via histone deacetylase (HDAC) inhibitors and histone acetyltransferases may enhance hippocampal synaptic plasticity and hippocampus-dependent memory. Little is known about the effects of HDAC inhibitors on extinction, a learning process through which the ability of a previously conditioned stimulus, such as a conditioning context, to evoke a conditioned response is diminished. The authors demonstrate that administration of the HDAC inhibitors sodium butyrate (NaB) systemically or trichostatin A (TSA) intrahippocampally prior to a brief (3-min) contextual extinction session causes context-evoked fear to decrease to levels observed with a long (24-min) extinction session. These results suggest that HDAC inhibitors may enhance learning during extinction and are consistent with other studies demonstrating a role for the hippocampus in contextual extinction. Molecular and behavioral mechanisms through which this enhanced extinction effect may occur are discussed. PMID:17907845

  20. The effect of phosphodiesterase inhibitors on the extinction of cocaine-induced conditioned place preference in mice.

    Science.gov (United States)

    Liddie, Shervin; Anderson, Karen L; Paz, Andres; Itzhak, Yossef

    2012-10-01

    Several phosphodiesterase inhibitors (PDEis) improve cognition, suggesting that an increase in brain cAMP and cGMP facilitates learning and memory. Since extinction of drug-seeking behavior requires associative learning, consolidation and formation of new memory, the present study investigated the efficacy of three different PDEis in the extinction of cocaine-induced conditioned place preference (CPP) in B6129S mice. Mice were conditioned by escalating doses of cocaine which was resistant to extinction by free exploration. Immediately following each extinction session mice received (a) saline/vehicle, (b) rolipram (PDE4 inhibitor), (c) BAY-73-6691 (PDE9 inhibitor) or (d) papaverine (PDE10A inhibitor). Mice that received saline/vehicle during extinction training showed no reduction in CPP for >10 days. BAY-73-6691 (a) dose-dependently increased cGMP in hippocampus and amygdala, (b) significantly facilitated extinction and (c) diminished the reinstatement of cocaine CPP. Rolipram, which selectively increased brain cAMP levels, and papaverine which caused increases in both cAMP and cGMP levels, had no significant effect on the extinction of cocaine CPP. The results suggest that increase in hippocampal and amygdalar cGMP levels via blockade of PDE9 has a prominent role in the consolidation of extinction learning. PMID:22596207

  1. Neanderthal extinction by competitive exclusion.

    Directory of Open Access Journals (Sweden)

    William E Banks

    Full Text Available BACKGROUND: Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH. METHODOLOGY/PRINCIPAL FINDINGS: We apply a new methodology integrating archaeological and chronological data with high-resolution paleoclimatic simulations to define eco-cultural niches associated with Neanderthal and AMH adaptive systems during alternating cold and mild phases of Marine Isotope Stage 3. Our results indicate that Neanderthals and AMH exploited similar niches, and may have continued to do so in the absence of contact. CONCLUSIONS/SIGNIFICANCE: The southerly contraction of Neanderthal range in southwestern Europe during Greenland Interstadial 8 was not due to climate change or a change in adaptation, but rather concurrent AMH geographic expansion appears to have produced competition that led to Neanderthal extinction.

  2. Extinction, Relapse, and Behavioral Momentum

    OpenAIRE

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-01-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus–reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus–reinforcer relations. In this paper...

  3. Optimising Extinction of Conditioned Disgust.

    Science.gov (United States)

    Bosman, Renske C; Borg, Charmaine; de Jong, Peter J

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might be explained by disgust's adaptive function to motivate avoidance from contamination threats (pathogens) that cannot be readily detected and are invisible to the naked eye. Therefore, the mere visual presentation of unreinforced disgust eliciting stimuli might not be sufficient to correct a previously acquired threat value of the CS+. Following this, the current study tested whether the efficacy of CS-only exposure can be improved by providing additional safety information about the CS+. For the CSs we included two neutral items a pea soup and a sausage roll, whereas for the Unconditioned Stimulus (US) we used one video clip of a woman vomiting and a neutral one about glass blowing. The additional safety information was conveyed by allowing actual contact with the CS+ or by observing an actress eating the food items representing the CS+. When additional safety information was provided via allowing direct contact with the CS+, there was a relatively strong post-extinction increase in participants' willingness-to-eat the CS+. This beneficial effect was still evident at one-week follow up. Also self-reported disgust was lower at one-week follow up when additional safety information was provided. The current findings help explain why disgust is relatively insensitive to CS-only extinction procedures, and provide helpful starting points to improve interventions that are aimed to reduce distress in disgust-related psychopathology. PMID:26849211

  4. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, Kostas A.; Borges, Paulo A. V.; Ladle, Richard J.;

    2010-01-01

    , to calculate realistic and ecologically-adjusted species-area relationships. The results reveal dramatic and hitherto unrecognized levels of extinction debt, as a result of the extensive destruction of the native forest:> 95%, in ... in the last 45 yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future...

  5. Dynamic competition between large-scale functional networks differentiates fear conditioning and extinction in humans.

    Science.gov (United States)

    Marstaller, Lars; Burianová, Hana; Reutens, David C

    2016-07-01

    The high evolutionary value of learning when to respond to threats or when to inhibit previously learned associations after changing threat contingencies is reflected in dedicated networks in the animal and human brain. Recent evidence further suggests that adaptive learning may be dependent on the dynamic interaction of meta-stable functional brain networks. However, it is still unclear which functional brain networks compete with each other to facilitate associative learning and how changes in threat contingencies affect this competition. The aim of this study was to assess the dynamic competition between large-scale networks related to associative learning in the human brain by combining a repeated differential conditioning and extinction paradigm with independent component analysis of functional magnetic resonance imaging data. The results (i) identify three task-related networks involved in initial and sustained conditioning as well as extinction, and demonstrate that (ii) the two main networks that underlie sustained conditioning and extinction are anti-correlated with each other and (iii) the dynamic competition between these two networks is modulated in response to changes in associative contingencies. These findings provide novel evidence for the view that dynamic competition between large-scale functional networks differentiates fear conditioning from extinction learning in the healthy brain and suggest that dysfunctional network dynamics might contribute to learning-related neuropsychiatric disorders. PMID:27079532

  6. Global Extinction in Spiral Galaxies

    CERN Document Server

    Tully, R B; Huang, J S; Saunders, W J; Verheijen, M A W; Witchalls, P L

    1998-01-01

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in B,R,I and K' bands. Extinction causes systematic scatter in color-magnitude plots. A strong luminosity dependence is found. Relative edge-on to face-on extinction of up to 1.7 mag is found at B for the most luminous galaxies but is unmeasurably small for faint galaxies. At R the differential absorption with inclination reaches 1.3 mag, at I it reaches 1.0 mag, and at K' the differential absorption can in the extreme be as great as 0.3 mag. The luminosity dependence of reddening can be translated into a dependence on rotation rate which is a distance-independent observable. Hence, corrections can be made that are useful for distance measurements. The strong dependence of the corrections on luminosity act to steepen luminosity-linewidth correlations. The effect is greatest toward the blue, with...

  7. Quantification of extinction mechanism in counterflow premixed flames

    KAUST Repository

    Choi, Sangkyu

    2014-09-01

    The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H2, CH4, CH4+H2, CO+H2, and rich C3H8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H2, CH4, CH4+H2, CO+H2, and lean C3H8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H2 mixing to CO is found to be quite significant as compared to CH4+H2 cases, which can alter the flame behavior of CO flames to that of H2.

  8. Revisiting propranolol and PTSD: Memory erasure or extinction enhancement?

    Science.gov (United States)

    Giustino, Thomas F; Fitzgerald, Paul J; Maren, Stephen

    2016-04-01

    Posttraumatic stress disorder (PTSD) has been described as the only neuropsychiatric disorder with a known cause, yet effective behavioral and pharmacotherapies remain elusive for many afflicted individuals. PTSD is characterized by heightened noradrenergic signaling, as well as a resistance to extinction learning. Research aimed at promoting more effective treatment of PTSD has focused on memory erasure (disrupting reconsolidation) and/or enhancing extinction retention through pharmacological manipulations. Propranolol, a β-adrenoceptor antagonist, has received considerable attention for its therapeutic potential in PTSD, although its impact on patients is not always effective. In this review, we briefly examine the consequences of β-noradrenergic manipulations on both reconsolidation and extinction learning in rodents and in humans. We suggest that propranolol is effective as a fear-reducing agent when paired with behavioral therapy soon after trauma when psychological stress is high, possibly preventing or dampening the later development of PTSD. In individuals who have already suffered from PTSD for a significant period of time, propranolol may be less effective at disrupting reconsolidation of strong fear memories. Also, when PTSD has already developed, chronic treatment with propranolol may be more effective than acute intervention, given that individuals with PTSD tend to experience long-term, elevated noradrenergic hyperarousal.

  9. Extinction reveals that primary sensory cortex predicts reinforcement outcome.

    Science.gov (United States)

    Bieszczad, Kasia M; Weinberger, Norman M

    2012-02-01

    Primary sensory cortices are traditionally regarded as stimulus analysers. However, studies of associative learning-induced plasticity in the primary auditory cortex (A1) indicate involvement in learning, memory and other cognitive processes. For example, the area of representation of a tone becomes larger for stronger auditory memories and the magnitude of area gain is proportional to the degree that a tone becomes behaviorally important. Here, we used extinction to investigate whether 'behavioral importance' specifically reflects a sound's ability to predict reinforcement (reward or punishment) vs. to predict any significant change in the meaning of a sound. If the former, then extinction should reverse area gains as the signal no longer predicts reinforcement. Rats (n = 11) were trained to bar-press to a signal tone (5.0 kHz) for water-rewards, to induce signal-specific area gains in A1. After subsequent withdrawal of reward, A1 was mapped to determine representational areas. Signal-specific area gains, estimated from a previously established brain-behavior quantitative function, were reversed, supporting the 'reinforcement prediction' hypothesis. Area loss was specific to the signal tone vs. test tones, further indicating that withdrawal of reinforcement, rather than unreinforced tone presentation per se, was responsible for area loss. Importantly, the amount of area loss was correlated with the amount of extinction (r = 0.82, P reinforcement, and that the number of cells tuned to a stimulus can dictate its ability to command behavior.

  10. Extinction reveals that primary sensory cortex predicts reinforcement outcome.

    Science.gov (United States)

    Bieszczad, Kasia M; Weinberger, Norman M

    2012-02-01

    Primary sensory cortices are traditionally regarded as stimulus analysers. However, studies of associative learning-induced plasticity in the primary auditory cortex (A1) indicate involvement in learning, memory and other cognitive processes. For example, the area of representation of a tone becomes larger for stronger auditory memories and the magnitude of area gain is proportional to the degree that a tone becomes behaviorally important. Here, we used extinction to investigate whether 'behavioral importance' specifically reflects a sound's ability to predict reinforcement (reward or punishment) vs. to predict any significant change in the meaning of a sound. If the former, then extinction should reverse area gains as the signal no longer predicts reinforcement. Rats (n = 11) were trained to bar-press to a signal tone (5.0 kHz) for water-rewards, to induce signal-specific area gains in A1. After subsequent withdrawal of reward, A1 was mapped to determine representational areas. Signal-specific area gains, estimated from a previously established brain-behavior quantitative function, were reversed, supporting the 'reinforcement prediction' hypothesis. Area loss was specific to the signal tone vs. test tones, further indicating that withdrawal of reinforcement, rather than unreinforced tone presentation per se, was responsible for area loss. Importantly, the amount of area loss was correlated with the amount of extinction (r = 0.82, P reinforcement, and that the number of cells tuned to a stimulus can dictate its ability to command behavior. PMID:22304434

  11. Sex differences in learning processes of classical and operant conditioning.

    Science.gov (United States)

    Dalla, Christina; Shors, Tracey J

    2009-05-25

    Males and females learn and remember differently at different times in their lives. These differences occur in most species, from invertebrates to humans. We review here sex differences as they occur in laboratory rodent species. We focus on classical and operant conditioning paradigms, including classical eyeblink conditioning, fear-conditioning, active avoidance and conditioned taste aversion. Sex differences have been reported during acquisition, retention and extinction in most of these paradigms. In general, females perform better than males in the classical eyeblink conditioning, in fear-potentiated startle and in most operant conditioning tasks, such as the active avoidance test. However, in the classical fear-conditioning paradigm, in certain lever-pressing paradigms and in the conditioned taste aversion, males outperform females or are more resistant to extinction. Most sex differences in conditioning are dependent on organizational effects of gonadal hormones during early development of the brain, in addition to modulation by activational effects during puberty and adulthood. Critically, sex differences in performance account for some of the reported effects on learning and these are discussed throughout the review. Because so many mental disorders are more prevalent in one sex than the other, it is important to consider sex differences in learning when applying animal models of learning for these disorders. Finally, we discuss how sex differences in learning continue to alter the brain throughout the lifespan. Thus, sex differences in learning are not only mediated by sex differences in the brain, but also contribute to them.

  12. The ethics of reviving long extinct species.

    Science.gov (United States)

    Sandler, Ronald

    2014-04-01

    There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable. PMID:24372907

  13. Extinction and reinstatement of phasic dopamine signals in the nucleus accumbens core during Pavlovian conditioning.

    Science.gov (United States)

    Sunsay, Ceyhun; Rebec, George V

    2014-10-01

    The prediction-error model of dopamine (DA) signaling has largely been confirmed with various appetitive Pavlovian conditioning procedures and has been supported in tests of Pavlovian extinction. Studies have repeatedly shown, however, that extinction does not erase the original memory of conditioning as the prediction-error model presumes, putting the model at odds with contemporary views that treat extinction as an episode of learning rather than unlearning of conditioning. Here, we combined fast-scan cyclic voltammetry (FSCV) with appetitive Pavlovian conditioning to assess DA release directly during extinction and reinstatement. DA was monitored in the nucleus accumbens core, which plays a key role in reward processing. Following at least 4 daily sessions of 16 tone-food pairings, fast-scan cyclic voltammetry was performed while rats received additional tone-food pairings followed by tone alone presentations (i.e., extinction). Acquisition memory was reinstated with noncontingent presentations of reward and then tested with cue presentation. Tone-food pairings produced transient (1- to 3-s) DA release in response to tone. During extinction, the amplitude of the DA response decreased significantly. Following presentation of 2 noncontingent food pellets, subsequent tone presentation reinstated the DA signal. Our results support the prediction-error model for appetitive Pavlovian extinction but not for reinstatement.

  14. Sexual selection protects against extinction.

    Science.gov (United States)

    Lumley, Alyson J; Michalczyk, Łukasz; Kitson, James J N; Spurgin, Lewis G; Morrison, Catriona A; Godwin, Joanne L; Dickinson, Matthew E; Martin, Oliver Y; Emerson, Brent C; Chapman, Tracey; Gage, Matthew J G

    2015-06-25

    Reproduction through sex carries substantial costs, mainly because only half of sexual adults produce offspring. It has been theorized that these costs could be countered if sex allows sexual selection to clear the universal fitness constraint of mutation load. Under sexual selection, competition between (usually) males and mate choice by (usually) females create important intraspecific filters for reproductive success, so that only a subset of males gains paternity. If reproductive success under sexual selection is dependent on individual condition, which is contingent to mutation load, then sexually selected filtering through 'genic capture' could offset the costs of sex because it provides genetic benefits to populations. Here we test this theory experimentally by comparing whether populations with histories of strong versus weak sexual selection purge mutation load and resist extinction differently. After evolving replicate populations of the flour beetle Tribolium castaneum for 6 to 7 years under conditions that differed solely in the strengths of sexual selection, we revealed mutation load using inbreeding. Lineages from populations that had previously experienced strong sexual selection were resilient to extinction and maintained fitness under inbreeding, with some families continuing to survive after 20 generations of sib × sib mating. By contrast, lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines under inbreeding, and all were extinct after generation 10. Multiple mutations across the genome with individually small effects can be difficult to clear, yet sum to a significant fitness load; our findings reveal that sexual selection reduces this load, improving population viability in the face of genetic stress. PMID:25985178

  15. Controlled cortical impact before or after fear conditioning does not affect fear extinction in mice.

    Science.gov (United States)

    Sierra-Mercado, Demetrio; McAllister, Lauren M; Lee, Christopher C H; Milad, Mohammed R; Eskandar, Emad N; Whalen, Michael J

    2015-05-01

    Post-traumatic stress disorder (PTSD) is characterized in part by impaired extinction of conditioned fear. Traumatic brain injury (TBI) is thought to be a risk factor for development of PTSD. We tested the hypothesis that controlled cortical impact (CCI) would impair extinction of fear learned by Pavlovian conditioning, in mice. To mimic the scenarios in which TBI occurs prior to or after exposure to an aversive event, severe CCI was delivered to the left parietal cortex at one of two time points: (1) Prior to fear conditioning, or (2) after conditioning. Delay auditory conditioning was achieved by pairing a tone with a foot shock in "context A". Extinction training involved the presentation of tones in a different context (context B) in the absence of foot shock. Test for extinction memory was achieved by presentation of additional tones alone in context B over the following two days. In pre- or post-injury paradigms, CCI did not influence fear learning and extinction. Furthermore, CCI did not affect locomotor activity or elevated plus maze testing. Our results demonstrate that, within the time frame studied, CCI does not impair the acquisition and expression of conditioned fear or extinction memory. PMID:25721797

  16. Controlled cortical impact before or after fear conditioning does not affect fear extinction in mice.

    Science.gov (United States)

    Sierra-Mercado, Demetrio; McAllister, Lauren M; Lee, Christopher C H; Milad, Mohammed R; Eskandar, Emad N; Whalen, Michael J

    2015-05-01

    Post-traumatic stress disorder (PTSD) is characterized in part by impaired extinction of conditioned fear. Traumatic brain injury (TBI) is thought to be a risk factor for development of PTSD. We tested the hypothesis that controlled cortical impact (CCI) would impair extinction of fear learned by Pavlovian conditioning, in mice. To mimic the scenarios in which TBI occurs prior to or after exposure to an aversive event, severe CCI was delivered to the left parietal cortex at one of two time points: (1) Prior to fear conditioning, or (2) after conditioning. Delay auditory conditioning was achieved by pairing a tone with a foot shock in "context A". Extinction training involved the presentation of tones in a different context (context B) in the absence of foot shock. Test for extinction memory was achieved by presentation of additional tones alone in context B over the following two days. In pre- or post-injury paradigms, CCI did not influence fear learning and extinction. Furthermore, CCI did not affect locomotor activity or elevated plus maze testing. Our results demonstrate that, within the time frame studied, CCI does not impair the acquisition and expression of conditioned fear or extinction memory.

  17. Microwave extinction characteristics of nanoparticle aggregates

    Science.gov (United States)

    Wu, Y. P.; Cheng, J. X.; Liu, X. X.; Wang, H. X.; Zhao, F. T.; Wen, W. W.

    2016-07-01

    Structure of nanoparticle aggregates plays an important role in microwave extinction capacity. The diffusion-limited aggregation model (DLA) for fractal growth is utilized to explore the possible structures of nanoparticle aggregates by computer simulation. Based on the discrete dipole approximation (DDA) method, the microwave extinction performance by different nano-carborundum aggregates is numerically analyzed. The effects of the particle quantity, original diameter, fractal structure, as well as orientation on microwave extinction are investigated, and also the extinction characteristics of aggregates are compared with the spherical nanoparticle in the same volume. Numerical results give out that proper aggregation of nanoparticle is beneficial to microwave extinction capacity, and the microwave extinction cross section by aggregated granules is better than that of the spherical solid one in the same volume.

  18. Presence and Acquired Origin of Reduced Recall for Fear Extinction in PTSD: Results of a Twin Study

    Science.gov (United States)

    Milad, Mohammed R.; Orr, Scott P.; Lasko, Natasha B.; Chang, Yuchiao; Rauch, Scott L.; Pitman, Roger K.

    2008-01-01

    Recall of fear extinction, which is thought to aid in recovery from a psychologically traumatic event, is hypothesized to be deficient in post-traumatic stress disorder (PTSD), but this has not yet been demonstrated in the laboratory, nor has its origin been investigated. To address these two issues, 14 pairs of monozygotic twins discordant for combat exposure, in 7 of which the combat-exposed twin had PTSD, underwent a two-day fear conditioning and extinction procedure. On Day 1, subjects viewed colored light conditioned stimuli, some of which were paired with mild electric shock, followed by extinction of the conditioned responses. On Day 2, recall of Day 1 extinction learning (i.e., extinction retention) was assessed. Skin conductance response (SCR) was the dependent measure. There were no group differences during acquisition or extinction learning. However, a significant PTSD Diagnosis (in the exposed twin) x combat Exposure interaction emerged during extinction recall, with the PTSD combat veterans having larger SCRs than their own co-twins, and than the non-PTSD combat veterans and their co-twins. These results indicate that retention of extinction of conditioned fear is deficient in PTSD. Furthermore, they support the conclusion that this deficit is acquired as a result of combat trauma leading to PTSD, rather than being a predisposing factor to developing PTSD upon the stress of combat. PMID:18313695

  19. Methylphenidate enhances extinction of contextual fear

    OpenAIRE

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show that MPH, administered before or immediately following extinction of contextual fear, will enhance extinction retention in C57BL/6 mice. Animals that ...

  20. Extinction Maps in the WFAU Archives

    CERN Document Server

    Cross, Nicholas

    2015-01-01

    A brief set of notes about the database design for 3D maps of dust extinction in the WFAU Archives, which support data from UKIRT-WFCAM, VISTA and VST. The notes also detail typical use cases, such as getting colour-excesses, extinction-corrections, spectral energy distributions and colour-magnitude diagrams and demonstrate the SQL queries to return data, along with examples from VVV DR2 with bulge extinction maps from Chen et al. (2013).

  1. Acquisition, Extinction, Recovery, and Reversal of Different Response Sequences Under Conditional Control by Nicotine in Rats

    Science.gov (United States)

    Troisi, Joseph R.

    2013-01-01

    Complex voluntary behaviors occur in sequence. Eight rats were trained in an operant procedure that used nicotine and non-drug (saline) states as interoceptive cues that signaled which of two behavioral sequences led to food reward. The distal and proximal responses in the chain were always maintained on variable interval 30-sec and fixed ratio-1 schedules, respectively, and rate differences between the responses were used as the dependent variable. Extinction and reversal training was conducted. Distal response rates were significantly greater than proximal response rates during training, testing, extinction, and reversal learning. These data suggest that (a) nicotine can establish interoceptive control over different response sequences, and (b) extinction of one response sequence may be state-dependent. The clinical relevance of extinction of complex behavioral repertoires such as drug-seeking and drug-taking behavior that are evoked by specific interoceptive cues is addressed in regard to drug abuse treatment and relapse. PMID:24837654

  2. Mass extinctions vs. uniformitarianism in biological evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bak, P.; Paczuski, M.

    1995-12-31

    It is usually believed that Darwin`s theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of co-evolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.

  3. Secondary extinction in Pavlovian fear conditioning.

    Science.gov (United States)

    Vurbic, Drina; Bouton, Mark E

    2011-09-01

    Pavlov (1927/1960) reported that following the conditioning of several stimuli, extinction of one conditioned stimulus (CS) attenuated responding to others that had not undergone direct extinction. However, this secondary extinction effect has not been widely replicated in the contemporary literature. In three conditioned suppression experiments with rats, we further explored the phenomenon. In Experiment 1, we asked whether secondary extinction is more likely to occur with target CSs that have themselves undergone some prior extinction. A robust secondary extinction effect was obtained with a nonextinguished target CS. Experiment 2 showed that extinction of one CS was sufficient to reduce renewal of a second CS when it was tested in a neutral (nonextinction) context. In Experiment 3, secondary extinction was observed in groups that initially received intermixed conditioning trials with the target and nontarget CSs, but not in groups that received conditioning of the two CSs in separate sessions. The results are consistent with the hypothesis that CSs must be associated with a common temporal context during conditioning for secondary extinction to occur.

  4. Extinction by Single and Multiple Particles

    Science.gov (United States)

    Berg, Matthew; Sorensen, Christopher; Chakrabarti, Amit

    2008-03-01

    The combined effect of scattering and absorption is referred to as extinction and is responsible for the redistribution of radiant energy by a particle. This presentation will show that extinction is due to wave interference. Simulations of the energy flow caused by the interference graphically demonstrate how extinction redistributes the energy of incident light. Both single and multi-particle systems are considered. A conceptual, phase-based explanation is given that builds on previous work and illustrates the physical meaning of the optical theorem. Implications regarding the measurement of extinction are discussed.

  5. Long-term maintenance of immediate or delayed extinction is determined by the extinction-test interval

    OpenAIRE

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively long extinction-test interval was used; a relatively short extinction-test interval yielded the opposite result (Experiment 2). Previous data appear co...

  6. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction.

    Directory of Open Access Journals (Sweden)

    Andrew Z Krug

    Full Text Available Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL as a proxy for phylogenetic clustering, we find that A both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns.

  7. Phylogenetically patterned speciation rates and extinction risks change the loss of evolutionary history during extinctions.

    OpenAIRE

    Heard, S B; Mooers, A O

    2000-01-01

    If we are to plan conservation strategies that minimize the loss of evolutionary history through human-caused extinctions, we must understand how this loss is related to phylogenetic patterns in current extinction risks and past speciation rates. Nee & May (1997, Science 278, 692-694) showed that for a randomly evolving clade (i) a single round of random extinction removed relatively little evolutionary history, and (ii) extinction management (choosing which taxa to sacrifice) offered only ma...

  8. Comparing counterconditioning and extinction as methods to reduce fear of movement-related pain

    NARCIS (Netherlands)

    Meulders, A.; Karsdorp, P.A.; Claes, N.; Vlaeyen, J.W.S.

    2015-01-01

    Cognitive-behavioral treatments for chronic pain typically target pain-related fear; exposure in vivo is a common treatment focusing on disconfirming harm expectancy of feared movements. Exposure therapy is tailored on Pavlovian extinction; an alternative fear reduction technique that also alters st

  9. Press/Pulse: Explaining selective terrestrial extinctions at the Cretaceous/Palaeogene boundary

    Science.gov (United States)

    Arens, Nan Crystal

    2010-05-01

    Single-cause mass extinction scenarios require extreme conditions to generate sufficiently strong kill mechanisms. Such dire effects are commonly at odds with the taxonomic selectivity that characterizes most extinction events. In response, some researchers have proposed that the interaction of a variety of factors typify episodes of elevated extinction. Previous work (Arens & West 2008 Paleobiology 34:456-471) has shown that a combination of press and pulse disturbances increases the probability of elevated extinction. The press/pulse contrast is borrowed from community ecology, where researchers have long recognized that the ecological response to long-term stress differs from that of an instantaneous catastrophe. Scaled to the macroevolutionary level, press disturbances alter community composition by placing multigenerational stress on populations. Press disturbances do not necessarily cause mortality, but reduce population size by a variety of mechanisms such as curtailed reproduction. Pulse disturbances are sudden catastrophic events that cause extensive mortality. Either press or pulse disturbances of sufficient magnitude can cause extinction, however elevated extinction occurs more commonly during the coincidence of lower-magnitude press and pulse events. The Cretaceous/Palaeogene (K/P) extinction is one of the best examples of a press/pulse extinction. Deccan Trap volcanism, which straddled the K/P boundary, altered atmospheric composition and climate. This episodic volcanism likely contributed to the climate instability observed in terrestrial ecosystems and exerted press stress. Pulse disturbance was produced by bolide impact, which punctuated the end of the Cretaceous. The press/pulse mechanism also more effectively explains selectivity in terrestrial vertebrate and plant extinctions at the K/P boundary than do single-mechanisms scenarios. For example, why do environmentally sensitive vertebrates such as amphibians experience no extinction? And why do

  10. Mass extinction and the structure of the milky way

    Directory of Open Access Journals (Sweden)

    Filipović M.D.

    2013-01-01

    Full Text Available We use the most up-to-date Milky Way model and solar orbit data in order to test the hypothesis that the Sun's galactic spiral arm crossings cause mass extinction events on Earth. To do this, we created a new model of the Milky Way's spiral arms by combining a large quantity of data from several surveys. We then combined this model with a recently derived solution for the solar orbit to determine the timing of the Sun's historical passages through the Galaxy's spiral arms. Our new model was designed with a symmetrical appearance, with the major alteration being the addition of a spur at the far side of the Galaxy. A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy's various spiral arms. Also, we briefly discuss and combine previous work on the Galactic Habitable Zone with the new Milky Way model.

  11. Opioid receptors in the midbrain periaqueductal gray regulate extinction of pavlovian fear conditioning.

    Science.gov (United States)

    McNally, Gavan P; Pigg, Michael; Weidemann, Gabrielle

    2004-08-01

    Four experiments studied the role of opioid receptors in the midbrain periaqueductal gray matter (PAG), an important structure eliciting conditioned fear responses, in the extinction of Pavlovian fear. Rats received pairings of an auditory conditioned stimulus (CS) with a foot shock unconditioned stimulus (US). The freezing conditioned response (CR) elicited by the CS was then extinguished via nonreinforced presentations of the CS. Microinjection of the opioid receptor antagonist naloxone into the ventrolateral PAG (vlPAG) before nonrein-forced CS presentations impaired development of extinction, but such microinjections at the end of extinction did not reinstate an already extinguished freezing CR. This role for opioid receptors in fear extinction was specific to the vlPAG because infusions of naloxone into the dorsal PAG did not impair fear extinction. Finally, the impairment of fear extinction produced by vlPAG infusions of naloxone was dose-dependent. These results show for the first time that the midbrain PAG contributes to fear extinction and specifically identify a role for vlPAG opioid receptors in the acquisition but not the expression of such extinction. Taken together with our previous findings, we suggest that, during fear conditioning, activation of vlPAG opioid receptors contributes to detection of the discrepancy between the actual and expected outcome of the conditioning trial. vlPAG opioid receptors regulate the learning that accrues to the CS and other stimuli present on a trial because they instantiate an associative error correction process influencing US information reaching the site of CS-US convergence in the amygdala. During nonreinforcement, this vlPAG opioid receptor contribution signals extinction.

  12. The influence of partner cues on the extinction of causal judgments in people.

    Science.gov (United States)

    Holmes, Nathan M; Griffiths, Oren; Westbrook, R Frederick

    2014-09-01

    Studies in laboratory animals have shown that the extinction of a conditioned stimulus, A, is regulated by the associative history of a second stimulus, X, when the two are extinguished in simultaneous compound: An inhibitory X protects A from extinction (Rescorla Learning & Behavior, 31, 124-132, 2003), whereas an excitatory X facilitates, and under some circumstances deepens, the extinction of A (Rescorla Journal of Experimental Psychology: Animal Behavior Processes, 26, 251-260, 2000, Journal of Experimental Psychology: Animal Behavior Processes, 32, 135-144, 2006). In the present study, we used the allergist task to examine whether the extinction of causal judgments in people is similarly regulated by the causal status of co-present stimuli. Experiment 1 showed that a cue trained as a conditioned inhibitor protected a target cue from extinction: The target extinguished in compound with the inhibitor was rated as being more causal of the outcome than was a target extinguished in compound with a control cue lacking inhibitory properties. In contrast, the remaining experiments showed that the extinction of a target cue was regulated by the presence, but not the causal status, of a partner cue: Target cues extinguished in compound were protected from extinction, and no evidence showed that an already extinguished partner conferred more protection (Exp. 2), or that an excitatory partner conferred any less protection (Exps. 2 and 3), or that an excitatory partner deepened the extinction of its already extinguished target. These findings are inconsistent with elemental models that rely on a common error term to explain associative changes in extinction. They are largely, but not completely, consistent with the configural model proposed by Pearce (Psychological Review, 94, 61-73, 1987), which predicts an ordering of levels of protection that was not observed.

  13. Constraints on Enhanced Extinction Resulting from Extinction Treatment in the Presence of an Added Excitor

    Science.gov (United States)

    Urcelay, Gonzalo P.; Lipatova, Olga; Miller, Ralph R.

    2009-01-01

    Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects…

  14. Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans

    NARCIS (Netherlands)

    S.D. Norrholm; B. Vervliet; T. Jovanovic; W. Boshoven; K.M. Myers; M. Davis; B.O. Rothbaum; E.J. Duncan

    2008-01-01

    Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occu

  15. Orexin/hypocretin receptor 1 signaling mediates Pavlovian cue-food conditioning and extinction.

    Science.gov (United States)

    Keefer, Sara E; Cole, Sindy; Petrovich, Gorica D

    2016-08-01

    Learned food cues can drive feeding in the absence of hunger, and orexin/hypocretin signaling is necessary for this type of overeating. The current study examined whether orexin also mediates cue-food learning during the acquisition and extinction of these associations. In Experiment 1, rats underwent two sessions of Pavlovian appetitive conditioning, consisting of tone-food presentations. Prior to each session, rats received either the orexin 1 receptor antagonist SB-334867 (SB) or vehicle systemically. SB treatment did not affect conditioned responses during the first conditioning session, measured as food cup behavior during the tone and latency to approach the food cup after the tone onset, compared to the vehicle group. During the second conditioning session, SB treatment attenuated learning. All groups that received SB, prior to either the first or second conditioning session, displayed significantly less food cup behavior and had longer latencies to approach the food cup after tone onset compared to the vehicle group. These findings suggest orexin signaling at the 1 receptor mediates the consolidation and recall of cue-food acquisition. In Experiment 2, another group of rats underwent tone-food conditioning sessions (drug free), followed by two extinction sessions under either SB or vehicle treatment. Similar to Experiment 1, SB did not affect conditioned responses during the first session. During the second extinction session, the group that received SB prior to the first extinction session, but vehicle prior to the second, expressed conditioned food cup responses longer after tone offset, when the pellets were previously delivered during conditioning, and maintained shorter latencies to approach the food cup compared to the other groups. The persistence of these conditioned behaviors indicates impairment in extinction consolidation due to SB treatment during the first extinction session. Together, these results demonstrate an important role for orexin

  16. Combined Neuropeptide S and D-Cycloserine Augmentation Prevents the Return of Fear in Extinction-Impaired Rodents: Advantage of Dual versus Single Drug Approaches

    Science.gov (United States)

    Maurer, Verena; Murphy, Conor; Schmuckermair, Claudia; Muigg, Patrick; Neumann, Inga D.; Whittle, Nigel

    2016-01-01

    Background: Despite its success in treating specific anxiety disorders, the effect of exposure therapy is limited by problems with tolerability, treatment resistance, and fear relapse after initial response. The identification of novel drug targets facilitating fear extinction in clinically relevant animal models may guide improved treatment strategies for these disorders in terms of efficacy, acceleration of fear extinction, and return of fear. Methods: The extinction-facilitating potential of neuropeptide S, D-cycloserine, and a benzodiazepine was investigated in extinction-impaired high anxiety HAB rats and 129S1/SvImJ mice using a classical cued fear conditioning paradigm followed by extinction training and several extinction test sessions to study fear relapse. Results: Administration of D-cycloserine improved fear extinction in extinction-limited, but not in extinction-deficient, rodents compared with controls. Preextinction neuropeptide S caused attenuated fear responses in extinction-deficient 129S1/SvImJ mice at extinction training onset and further reduced freezing during this session. While the positive effects of either D-cycloserine or neuropeptide S were not persistent in 129S1/SvImJ mice after 10 days, the combination of preextinction neuropeptide S with postextinction D-cycloserine rendered the extinction memory persistent and context independent up to 5 weeks after extinction training. This dual pharmacological adjunct to extinction learning also protected against fear reinstatement in 129S1/SvImJ mice. Conclusions: By using the potentially nonsedative anxiolytic neuropeptide S and the cognitive enhancer D-cycloserine to facilitate deficient fear extinction, we provide here the first evidence of a purported efficacy of a dual over a single drug approach. This approach may render exposure sessions less aversive and more efficacious for patients, leading to enhanced protection from fear relapse in the long term. PMID:26625894

  17. A NMDA receptor antagonist, MK-801 impairs consolidating extinction of auditory conditioned fear responses in a Pavlovian model.

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    Jun-Li Liu

    Full Text Available BACKGROUND: In auditory fear conditioning, repeated presentation of the tone in the absence of shock leads to extinction of the acquired fear responses. The glutamate N-methyl-D-aspartate receptor (NMDAR is thought to be involved in the extinction of the conditioned fear responses, but its detailed role in initiating and consolidating or maintaining the fear extinction memory is unclear. Here we investigated this issue by using a NMDAR antagonist, MK-801. METHODS/MAIN FINDINGS: The effects of immediate (beginning at 10 min after the conditioning and delayed (beginning at 24 h after conditioning extinctions were first compared with the finding that delayed extinction caused a better and long-lasting (still significant on the 20(th day after extinction depression on the conditioned fear responses. In a second experiment, MK-801 was intraperitoneally (i.p. injected at 40 min before, 4 h or 12 h after the delayed extinction, corresponding to critical time points for initiating, consolidating or maintaining the fear extinction memory. i.p. injection of MK-801 at either 40 min before or 4 h after delayed extinction resulted in an impairment of initiating and consolidating fear extinction memory, which caused a long lasting increased freezing score that was still significant on the 7th day after extinction, compared with extinction group. However, MK-801 administered at 12 h after the delayed extinction, when robust consolidation has been occurred and stabilized, did not affect the established extinction memory. Furthermore, the changed freezing behaviors was not due to an alteration in general anxiety levels, since MK-801 treatment had no effect on the percentage of open-arm time or open-arm entries in an Elevated Plus Maze (EPM task. CONCLUSIONS/SIGNIFICANCE: Our data suggested that the activation of NMDARs plays important role in initiation and consolidation but not maintenance of fear extinction memory. Together with the fact that NMDA receptor is

  18. An allometric approach to quantify the extinction vulnerability of birds and mammals.

    Science.gov (United States)

    Hilbers, J P; Schipper, A M; Hendriks, A J; Verones, F; Pereira, H M; Huijbregts, M A J

    2016-03-01

    -specific information. The framework facilitates the estimation of extinction vulnerabilities of data-deficient species. It may be applied to forecast extinction vulnerability in response to a changing environment, by incorporating quantitative relationships between wildlife demographic parameters and environmental drivers like habitat alteration, climate change, or hunting.

  19. An allometric approach to quantify the extinction vulnerability of birds and mammals.

    Science.gov (United States)

    Hilbers, J P; Schipper, A M; Hendriks, A J; Verones, F; Pereira, H M; Huijbregts, M A J

    2016-03-01

    -specific information. The framework facilitates the estimation of extinction vulnerabilities of data-deficient species. It may be applied to forecast extinction vulnerability in response to a changing environment, by incorporating quantitative relationships between wildlife demographic parameters and environmental drivers like habitat alteration, climate change, or hunting. PMID:27197389

  20. Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate.

    Directory of Open Access Journals (Sweden)

    Paulo R Guimarães

    Full Text Available BACKGROUND: Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals > 10(3 kg, yet these dispersers were extinct in South America 10-15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics. METHODOLOGY/PRINCIPAL FINDINGS: We introduce an operational definition of megafaunal fruits and perform a comparative analysis of 103 Neotropical fruit species fitting this dispersal mode. We define two megafaunal fruit types based on previous analyses of elephant fruits: fruits 4-10 cm in diameter with up to five large seeds, and fruits > 10 cm diameter with numerous small seeds. Megafaunal fruits are well represented in unrelated families such as Sapotaceae, Fabaceae, Solanaceae, Apocynaceae, Malvaceae, Caryocaraceae, and Arecaceae and combine an overbuilt design (large fruit mass and size with either a single or few ( 100 seeds. Within-family and within-genus contrasts between megafaunal and non-megafaunal groups of species indicate a marked difference in fruit diameter and fruit mass but less so for individual seed mass, with a significant trend for megafaunal fruits to have larger seeds and seediness. CONCLUSIONS/SIGNIFICANCE: Megafaunal fruits allow plants to circumvent the trade-off between seed size and dispersal by relying on frugivores able to disperse enormous seed loads over long-distances. Present-day seed dispersal by scatter-hoarding rodents, introduced livestock, runoff, flooding, gravity, and human-mediated dispersal allowed survival of megafauna-dependent fruit species after extinction of the major seed dispersers. Megafauna extinction had several potential consequences, such as a scale shift reducing the seed dispersal distances, increasingly clumped spatial patterns, reduced geographic ranges and limited genetic variation and increased among

  1. Can Parallelingualism Save Norwegian from Extinction?

    Science.gov (United States)

    Linn, Andrew R.

    2010-01-01

    Language extinction is one of the most pressing issues in linguistics today, and the literature is full of discussion about how to combat it. Statements that Norwegian is amongst the languages that are already extinct are merely examples of a widespread tendency in the literature towards erroneous information about Norwegian. Nonetheless, there is…

  2. Mass extinctions: Ecological selectivity and primary production

    Science.gov (United States)

    Rhodes, Melissa Clark; Thayer, Charles W.

    1991-09-01

    If mass extinctions were caused by reduced primary productivity, then extinctions should be concentrated among animals with starvation-susceptible feeding modes, active lifestyles, and high-energy budgets. The stratigraphic ranges (by stage) of 424 genera of bivalves and 309 genera of articulate brachiopods suggest that there was an unusual reduction of primary productivity at the Cretaceous/Tertiary (K/T) boundary extinction. For bivalves at the K/T, there were (1) selective extinction of suspension feeders and other susceptible trophic categories relative to deposit feeders and other resistant categories, and (2) among suspension feed-ers, selective extinction of bivalves with active locomotion. During the Permian-Triassic (P/Tr) extinction and Jurassic background time, extinction rates among suspension feeders were greater for articulate brachiopods than for bivalves. But during the K/T event, extinction rates of articulates and suspension-feeding bivalves equalized, possibly because the low-energy budgets of articulates gave them an advantage when food was scarce.

  3. Current extinction rates of reptiles and amphibians.

    Science.gov (United States)

    Alroy, John

    2015-10-20

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats.

  4. TROPICAL MASS EXTINCTIONS AND THE SCIENTIFIC METHOD

    Science.gov (United States)

    Kangas (1992), Undiscovered species and the falsifiability of the tropical mass extinction hypotheses, ESA Bulletin 73:124-125, 1992, argues that there is a paradox concerning the mass extinctions projected from current rates of tropical deforestation. he parameters; for a given ...

  5. Periodicity of extinction: A 1988 update

    Science.gov (United States)

    Sepkowski, J. John, Jr.

    1988-01-01

    The hypothesis that events of mass extinction recur periodically at approximately 26 my intervals is an empirical claim based on analysis of data from the fossil record. The hypothesis has become closely linked with catastrophism because several events in the periodic series are associated with evidence of extraterrestrial impacts, and terrestrial forcing mechanisms with long, periodic recurrences are not easily conceived. Astronomical mechanisms that have been hypothesized include undetected solar companions and solar oscillation about the galactic plane, which induce comet showers and result in impacts on Earth at regular intervals. Because these mechanisms are speculative, they have been the subject of considerable controversy, as has the hypothesis of periodicity of extinction. In response to criticisms and uncertainties, a data base was developed on times of extinction of marine animal genera. A time series is given and analyzed with 49 sample points for the per-genus extinction rate from the Late Permian to the Recent. An unexpected pattern in the data is the uniformity of magnitude of many of the periodic extinction events. Observations suggest that the sequence of extinction events might be the result of two sets of mechanisms: a periodic forcing that normally induces only moderate amounts of extinction, and independent incidents or catastrophes that, when coincident with the periodic forcing, amplify its signal and produce major-mass extinctions.

  6. Extinction-Induced Variability in Human Behavior

    Science.gov (United States)

    Kinloch, Jennifer M.; Foster, T. Mary; McEwan, James S. A.

    2009-01-01

    Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996);…

  7. Immediate extinction promotes the return of fear.

    Science.gov (United States)

    Merz, Christian J; Hamacher-Dang, Tanja C; Wolf, Oliver T

    2016-05-01

    Accumulating evidence indicates that immediate extinction is less effective than delayed extinction in attenuating the return of fear. This line of fear conditioning research impacts the proposed onset of psychological interventions after threatening situations. In the present study, forty healthy men were investigated in a differential fear conditioning paradigm with fear acquisition in context A, extinction in context B, followed by retrieval testing in both contexts 24h later to test fear renewal. Differently coloured lights served as conditioned stimuli (CS): two CS (CS+) were paired with an electrical stimulation that served as unconditioned stimulus, the third CS was never paired (CS-). Extinction took place immediately after fear acquisition or 24h later. One CS+ was extinguished whereas the second CS+ remained unextinguished to control for different time intervals between fear acquisition and retrieval testing. Immediate extinction led to larger skin conductance responses during fear retrieval to both the extinguished and unextinguished CS relative to the CS-, indicating a stronger return of fear compared to delayed extinction. Taken together, immediate extinction is less potent than delayed extinction and is associated with a stronger renewal effect. Thus, the time-point of psychological interventions relative to the offset of threatening situations needs to be carefully considered to prevent relapses. PMID:26995309

  8. Long-Term Maintenance of Immediate or Delayed Extinction Is Determined by the Extinction-Test Interval

    Science.gov (United States)

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively…

  9. The contextual brain: implications for fear conditioning, extinction and psychopathology

    Science.gov (United States)

    Maren, Stephen; Phan, K. Luan; Liberzon, Israel

    2016-01-01

    Contexts surround and imbue meaning to events; they are essential for recollecting the past, interpreting the present and anticipating the future. Indeed, the brain’s capacity to contextualize information permits enormous cognitive and behavioural flexibility. Studies of Pavlovian fear conditioning and extinction in rodents and humans suggest that a neural circuit including the hippocampus, amygdala and medial prefrontal cortex is involved in the learning and memory processes that enable context-dependent behaviour. Dysfunction in this network may be involved in several forms of psychopathology, including post-traumatic stress disorder, schizophrenia and substance abuse disorders. PMID:23635870

  10. Deep-time phylogenetic clustering of extinctions in an evolutionarily dynamic clade (Early Jurassic ammonites.

    Directory of Open Access Journals (Sweden)

    Clotilde Hardy

    Full Text Available Conservation biologists and palaeontologists are increasingly investigating the phylogenetic distribution of extinctions and its evolutionary consequences. However, the dearth of palaeontological studies on that subject and the lack of methodological consensus hamper our understanding of that major evolutionary phenomenon. Here we address this issue by (i reviewing the approaches used to quantify the phylogenetic selectivity of extinctions and extinction risks; (ii investigating with a high-resolution dataset whether extinctions and survivals were phylogenetically clustered among early Pliensbachian (Early Jurassic ammonites; (iii exploring the phylogenetic and temporal maintenance of this signal. We found that ammonite extinctions were significantly clumped phylogenetically, a pattern that prevailed throughout the 6.6 Myr-long early Pliensbachian interval. Such a phylogenetic conservatism did not alter--or may even have promoted--the evolutionary success of this major cephalopod clade. However, the comparison of phylogenetic autocorrelation among studies remains problematic because the notion of phylogenetic conservatism is scale-dependent and the intensity of the signal is sensitive to temporal resolution. We recommend a combined use of Moran's I, Pearson's ϕ and Fritz and Purvis' D statistics because they highlight different facets of the phylogenetic pattern of extinctions and/or survivals.

  11. Climate predictors of late quaternary extinctions

    DEFF Research Database (Denmark)

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram;

    2010-01-01

    of greater magnitudes during the Late Quaternary, witnessed more extinctions than continents with lower climate footprint values, with the exception of South America. Our results are consistent across species with different body masses, reinforcing the view that past climate changes contributed to global......Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...

  12. Enhancing Divergent Search through Extinction Events

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    A challenge in evolutionary computation is to create representations as evolvable as those in natural evolution. This paper hypothesizes that extinction events, i.e. mass extinctions, can significantly increase evolvability, but only when combined with a divergent search algorithm, i.e. a search...... driven towards diversity (instead of optimality). Extinctions amplify diversity-generation by creating unpredictable evolutionary bottlenecks. Persisting through multiple such bottlenecks is more likely for lineages that diversify across many niches, resulting in indirect selection pressure...... for the capacity to evolve. This hypothesis is tested through experiments in two evolutionary robotics domains. The results show that combining extinction events with divergent search increases evolvability, while combining them with convergent search offers no similar benefit. The conclusion is that extinction...

  13. Invasions and extinctions reshape coastal marine food webs.

    Science.gov (United States)

    Byrnes, Jarrett E; Reynolds, Pamela L; Stachowicz, John J

    2007-01-01

    The biodiversity of ecosystems worldwide is changing because of species loss due to human-caused extinctions and species gain through intentional and accidental introductions. Here we show that the combined effect of these two processes is altering the trophic structure of food webs in coastal marine systems. This is because most extinctions ( approximately 70%) occur at high trophic levels (top predators and other carnivores), while most invasions are by species from lower trophic levels (70% macroplanktivores, deposit feeders, and detritivores). These opposing changes thus alter the shape of marine food webs from a trophic pyramid capped by a diverse array of predators and consumers to a shorter, squatter configuration dominated by filter feeders and scavengers. The consequences of the simultaneous loss of diversity at top trophic levels and gain at lower trophic levels is largely unknown. However, current research suggests that a better understanding of how such simultaneous changes in diversity can impact ecosystem function will be required to manage coastal ecosystems and forecast future changes. PMID:17356703

  14. A Unifying Model of the Role of the Infralimbic Cortex in Extinction and Habits

    Science.gov (United States)

    Barker, Jacqueline M.; Taylor, Jane R.; Chandler, L. Judson

    2014-01-01

    The infralimbic prefrontal cortex (IL) has been shown to be critical for the regulation of flexible behavior, but its precise function remains unclear. This region has been shown to be critical for the acquisition, consolidation, and expression of extinction learning, leading many to hypothesize that IL suppresses behavior as part of a…

  15. The Histone Deacetylase Inhibitor Valproic Acid Enhances Acquisition, Extinction, and Reconsolidation of Conditioned Fear

    Science.gov (United States)

    Bredy, Timothy W.; Barad, Mark

    2008-01-01

    Histone modifications contribute to the epigenetic regulation of gene expression, a process now recognized to be important for the consolidation of long-term memory. Valproic acid (VPA), used for many years as an anticonvulsant and a mood stabilizer, has effects on learning and memory and enhances the extinction of conditioned fear through its…

  16. Sleep and REM sleep disturbance in the pathophysiology of PTSD: the role of extinction memory.

    Science.gov (United States)

    Pace-Schott, Edward F; Germain, Anne; Milad, Mohammed R

    2015-01-01

    Post-traumatic stress disorder (PTSD) is accompanied by disturbed sleep and an impaired ability to learn and remember extinction of conditioned fear. Following a traumatic event, the full spectrum of PTSD symptoms typically requires several months to develop. During this time, sleep disturbances such as insomnia, nightmares, and fragmented rapid eye movement sleep predict later development of PTSD symptoms. Only a minority of individuals exposed to trauma go on to develop PTSD. We hypothesize that sleep disturbance resulting from an acute trauma, or predating the traumatic experience, may contribute to the etiology of PTSD. Because symptoms can worsen over time, we suggest that continued sleep disturbances can also maintain and exacerbate PTSD. Sleep disturbance may result in failure of extinction memory to persist and generalize, and we suggest that this constitutes one, non-exclusive mechanism by which poor sleep contributes to the development and perpetuation of PTSD. Also reviewed are neuroendocrine systems that show abnormalities in PTSD, and in which stress responses and sleep disturbance potentially produce synergistic effects that interfere with extinction learning and memory. Preliminary evidence that insomnia alone can disrupt sleep-dependent emotional processes including consolidation of extinction memory is also discussed. We suggest that optimizing sleep quality following trauma, and even strategically timing sleep to strengthen extinction memories therapeutically instantiated during exposure therapy, may allow sleep itself to be recruited in the treatment of PTSD and other trauma and stress-related disorders. PMID:26034578

  17. Sex differences in extinction recall in posttraumatic stress disorder: a pilot fMRI study.

    Science.gov (United States)

    Shvil, Erel; Sullivan, Gregory M; Schafer, Scott; Markowitz, John C; Campeas, Miriam; Wager, Tor D; Milad, Mohammed R; Neria, Yuval

    2014-09-01

    Recent research has found that individuals with posttraumatic stress disorder (PTSD) exhibit an impaired memory of fear extinction compounded by deficient functional activation of key nodes of the fear network including the amygdala, hippocampus, ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (dACC). Research has shown these regions are sexually dimorphic and activate differentially in healthy men and women during fear learning tasks. To explore biological markers of sex differences following exposure to psychological trauma, we used a fear learning and extinction paradigm together with functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) to assess 31 individuals with PTSD (18 women; 13 men) and 25 matched trauma-exposed healthy control subjects (13 women; 12 men). Whereas no sex differences appeared within the trauma-exposed healthy control group, both psychophysiological and neural activation patterns within the PTSD group indicated deficient recall of extinction memory among men and not among women. Men with PTSD exhibited increased activation in the left rostral dACC during extinction recall compared with women with PTSD. These findings highlight the importance of tracking sex differences in fear extinction when characterizing the underlying neurobiological mechanisms of PTSD psychopathology. PMID:24560771

  18. The Extinction Law in an Occulting Galaxy

    CERN Document Server

    Berlind, Andreas A; Pogge, R W; Sellgren, K; Berlind, Andreas A.

    1997-01-01

    We measure the extinction law in a galaxy's spiral arm and interarm regions using a visual and infrared (BVRJHK) imaging study of the interacting galaxies NGC 2207 and IC 2163. This is an overlapping spiral galaxy pair in which NGC 2207 partially occults IC 2163. This geometry enables us to directly measure the extinction of light from the background galaxy as it passes through the disk of the foreground galaxy. We measure the extinction as a function of wavelength, and find that there is less extinction in the optical bands than expected from a normal Galactic extinction law. This deviation is significantly larger in the interarm region than in the spiral arm. The extinction curve in the spiral arm resembles a Milky Way $R_V=5.0$ dust model and the interarm extinction curve is flatter (``greyer'') still. We examine the effect of scattering of background galaxy light into the line of sight and find that it is negligible. We also examine the effect of an unresolved patchy dust distribution using a simple two-c...

  19. Inhibition of spontaneous recovery of fear by mGluR5 after prolonged extinction training.

    Directory of Open Access Journals (Sweden)

    Sheng-Chun Mao

    Full Text Available Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged extinction training causes greater reduction in both fear-potentiated startle and spontaneous recovery. This effect was specifically blocked by metabotropic glutamate receptor 5 (mGluR5, but not by mGluR1 antagonists and by a protein synthesis inhibitor. Similar inhibition of memory recovery following prolonged extinction training was also observed in mice. In agreement with the instrumental role of mGluR5 in the prolonged inhibition of fear recovery, we found that FMR1-/- mice which exhibit enhanced mGluR5-mediated signaling exhibit lower spontaneous recovery of fear after extinction training than wild-type littermates. At the molecular level, we discovered that prolonged extinction training reversed the fear conditioning-induced increase in surface expression of GluR1, AMPA/NMDA ratio, postsynaptic density-95 (PSD-95 and synapse-associated protein-97 (SAP97. Accordingly, delivery of Tat-GluR2(3Y, a synthetic peptide that blocks AMPA receptor endocytosis, inhibited prolonged extinction training-induced inhibition of fear recovery. Together, our results demonstrate that prolonged extinction training results in the mGluR5-dependent long-term inhibition of fear recovery. This effect may involve the degradation of original memory and may explain the beneficial effects of prolonged exposure therapy for the treatment of phobias.

  20. Effect of continuous and partial reinforcement on the acquisition and extinction of human conditioned fear.

    Science.gov (United States)

    Grady, Ashley K; Bowen, Kenton H; Hyde, Andrew T; Totsch, Stacie K; Knight, David C

    2016-02-01

    Extinction of Pavlovian conditioned fear in humans is a popular paradigm often used to study learning and memory processes that mediate anxiety-related disorders. Fear extinction studies often only pair the conditioned stimulus (CS) and unconditioned stimulus (UCS) on a subset of acquisition trials (i.e., partial reinforcement/pairing) to prolong extinction (i.e., partial reinforcement extinction effect; PREE) and provide more time to study the process. However, there is limited evidence that the partial pairing procedures typically used during fear conditioning actually extend the extinction process, while there is strong evidence these procedures weaken conditioned response (CR) acquisition. Therefore, determining conditioning procedures that support strong CR acquisition and that also prolong the extinction process would benefit the field. The present study investigated 4 separate CS-UCS pairing procedures to determine methods that support strong conditioning and that also exhibit a PREE. One group (C-C) of participants received continuous CS-UCS pairings; a second group (C-P) received continuous followed by partial CS-UCS pairings; a third group (P-C) received partial followed by continuous CS-UCS pairings; and a fourth group (P-P) received partial CS-UCS pairings during acquisition. A strong skin conductance CR was expressed by C-C and P-C groups but not by C-P and P-P groups at the end of the acquisition phase. The P-C group maintained the CR during extinction. In contrast, the CR extinguished quickly within the C-C group. These findings suggest that partial followed by continuous CS-UCS pairings elicit strong CRs and prolong the extinction process following human fear conditioning.

  1. Effect of continuous and partial reinforcement on the acquisition and extinction of human conditioned fear.

    Science.gov (United States)

    Grady, Ashley K; Bowen, Kenton H; Hyde, Andrew T; Totsch, Stacie K; Knight, David C

    2016-02-01

    Extinction of Pavlovian conditioned fear in humans is a popular paradigm often used to study learning and memory processes that mediate anxiety-related disorders. Fear extinction studies often only pair the conditioned stimulus (CS) and unconditioned stimulus (UCS) on a subset of acquisition trials (i.e., partial reinforcement/pairing) to prolong extinction (i.e., partial reinforcement extinction effect; PREE) and provide more time to study the process. However, there is limited evidence that the partial pairing procedures typically used during fear conditioning actually extend the extinction process, while there is strong evidence these procedures weaken conditioned response (CR) acquisition. Therefore, determining conditioning procedures that support strong CR acquisition and that also prolong the extinction process would benefit the field. The present study investigated 4 separate CS-UCS pairing procedures to determine methods that support strong conditioning and that also exhibit a PREE. One group (C-C) of participants received continuous CS-UCS pairings; a second group (C-P) received continuous followed by partial CS-UCS pairings; a third group (P-C) received partial followed by continuous CS-UCS pairings; and a fourth group (P-P) received partial CS-UCS pairings during acquisition. A strong skin conductance CR was expressed by C-C and P-C groups but not by C-P and P-P groups at the end of the acquisition phase. The P-C group maintained the CR during extinction. In contrast, the CR extinguished quickly within the C-C group. These findings suggest that partial followed by continuous CS-UCS pairings elicit strong CRs and prolong the extinction process following human fear conditioning. PMID:26692449

  2. Inhibition of spontaneous recovery of fear by mGluR5 after prolonged extinction training.

    Science.gov (United States)

    Mao, Sheng-Chun; Chang, Chih-Hua; Wu, Chia-Chen; Orejarena, M Juliana; Orejanera, Maria Juliana; Manzoni, Olivier J; Gean, Po-Wu

    2013-01-01

    Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged extinction training causes greater reduction in both fear-potentiated startle and spontaneous recovery. This effect was specifically blocked by metabotropic glutamate receptor 5 (mGluR5), but not by mGluR1 antagonists and by a protein synthesis inhibitor. Similar inhibition of memory recovery following prolonged extinction training was also observed in mice. In agreement with the instrumental role of mGluR5 in the prolonged inhibition of fear recovery, we found that FMR1-/- mice which exhibit enhanced mGluR5-mediated signaling exhibit lower spontaneous recovery of fear after extinction training than wild-type littermates. At the molecular level, we discovered that prolonged extinction training reversed the fear conditioning-induced increase in surface expression of GluR1, AMPA/NMDA ratio, postsynaptic density-95 (PSD-95) and synapse-associated protein-97 (SAP97). Accordingly, delivery of Tat-GluR2(3Y), a synthetic peptide that blocks AMPA receptor endocytosis, inhibited prolonged extinction training-induced inhibition of fear recovery. Together, our results demonstrate that prolonged extinction training results in the mGluR5-dependent long-term inhibition of fear recovery. This effect may involve the degradation of original memory and may explain the beneficial effects of prolonged exposure therapy for the treatment of phobias. PMID:23555716

  3. Marine carbon cycling following end Cretaceous extinction

    Science.gov (United States)

    Ridgwell, Andy; Thomas, Ellen; Alegret, Laia; Schmidt, Daniela

    2010-05-01

    Knowing how the transport of particulate organic carbon and associated nutrients into the ocean interior is controlled, is a prerequisite to reliable predictions of future changes in marine carbon cycling as the circulation and carbonate chemistry of the oceans are perturbed. Multiple mechanisms for particulate organic carbon transport have been proposed, most commonly based on sediment trap observations. Yet these observations primarily provide evidence for correlations between fluxes rather than being able to pin-point any particular mechanism. Despite this, global models tend to adopt one or other mechanism (e.g., ballasting) without independent justification. The geological record may help, as the evolution of pelagic ecosystems through the Phanerozoic has seen the emergence of animals (faecal pellets) and silicification and calcification of planktic organisms (ballasting), with evolutionary innovation fundamentally altering the nature of the oceanic biological pump. Moreover, catastrophic and transitory events, in which pelagic ecosystems were temporary disrupted, altering and biological pumping mechanisms, produced a tell-tale marine geochemical signature than may help elucidate the working of the biological pump. Here we focus on the bolide impact at the Cretaceous-Palaeogene boundary as it induced an enigmatic ‘collapse' in surface-to-deep carbon isotope (d13C) gradients, previously interpreted as representing a complete cessation of biological productivity and/or carbon pumping. Contemporaneous with this was a pronounced extinction of planktic calcifiers, resulting in an order of magnitude reduction in carbonate burial in deep-sea sediments. On face value, no (or little) carbonate ballasting and only a minor possible importance for dust together with ceased organic carbon transport to depth, is consistent with the existence of a dominant (carbonate) mineral ballasting mechanism prior to the event. However, a collapsed surface-to-deep d13C gradient does

  4. Volcanogenic Dark Matter and Mass Extinctions

    CERN Document Server

    Abbas, S; Abbas, Samar; Abbas, Afsar

    1996-01-01

    The passage of the Earth through dense clumps of dark matter, the presence of which are predicted by certain cosmologies, would produce large quantities of heat in the interior of this planet through the capture and subsequent annihilation of dark matter particles. This heat can cause large-scale volcanism which could in turn have caused the extinction of the dinosaurs and other mass extinctions. The periodicity of such volcanic outbursts agrees with the frequency of palaeontological mass extinctions as well as the observed periodicity in the occurrence of the largest flood basalt provinces on the globe.

  5. A mathematical model for Neanderthal extinction

    CERN Document Server

    Flores, J C

    1997-01-01

    A simple mathematical homogeneous model of competition is used to describe Neanderthal extinction in Europe. It considers two interacting species, Neanderthals and Early Modern Men, in the same ecological niche. Using paleontological data we claim that the parameter of similarity, between both species, fluctuates between 0.992 and 0.997. An extension of the model including migration (diffusion) is also discussed nevertheless, extinction of Neanderthal seems unavoidable. Numerical analysis of travelling wave solution (fronts) comfirms the extinction. The wave-front-velocity is estimated from linear analysis and numerical simulations confirm this estimation. We conjecture a mathematical formulation for the principle of exclusion between competitive interacting species (Gause).

  6. A model for evolution and extinction

    CERN Document Server

    Roberts, B W; Roberts, Bruce W

    1995-01-01

    We present a model for evolution and extinction in large ecosystems. The model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properties of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinctions and species lifetimes that we would expect to see in real ecosystems. It should be possible to test these predictions against the fossil record. The model indicates that a possible mechanism for mass extinction is the coincidence of a large coevolutionary avalanche in the ecosystem with a severe environmental disturbance.

  7. Pavlovian extinction, phobias, and the limits of the cognitive paradigm.

    Science.gov (United States)

    Furedy, J J; Riley, D M; Fredrikson, M

    1983-01-01

    The slow or total lack of decrease in some autonomic responses during extinction in aversive conditioning and concomitant verbalization of fear have remained a problem for learning theories and psychophysiology. Removal of the aversive stimulus should result in a rapid decrement in responding, as it does in cognitive and somatic systems. In laboratory analogues of phobia and clinical neurosis, however, such decreases do not occur in some autonomic responses and reported fear. In this article three areas of research are presented in which dissociations occur between cognitive and autonomic responses: 1) relational learning, 2) phobia, and 3) incubation. The data indicate that there are some important distinctions to be made concerning the properties of different psychological and physiological systems. These distinctions pertain to the differences between cognitive and noncognitive systems, between the two branches of the ANS, and between acquisition and extinction processes. These distinctions lead to a number of hypotheses concerning dissociations between response systems and have important implications for the understanding and treatment of neurosis.

  8. Activation of D1/5 Dopamine Receptors: A Common Mechanism for Enhancing Extinction of Fear and Reward-Seeking Behaviors.

    Science.gov (United States)

    Abraham, Antony D; Neve, Kim A; Lattal, K Matthew

    2016-07-01

    Dopamine is critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in appetitive tasks. A parallel and growing literature indicates that dopamine signaling is involved in consolidation of memories into stable representations in aversive tasks such as fear conditioning. Relatively little is known about how dopamine may modulate memories that form during extinction, when organisms learn that the relation between previously associated events is severed. We investigated whether fear and reward extinction share common mechanisms that could be enhanced with dopamine D1/5 receptor activation. Pharmacological activation of dopamine D1/5 receptors (with SKF 81297) enhanced extinction of both cued and contextual fear. These effects also occurred in the extinction of cocaine-induced conditioned place preference, suggesting that the observed effects on extinction were not specific to a particular type of procedure (aversive or appetitive). A cAMP/PKA biased D1 agonist (SKF 83959) did not affect fear extinction, whereas a broadly efficacious D1 agonist (SKF 83822) promoted fear extinction. Together, these findings show that dopamine D1/5 receptor activation is a target for the enhancement of fear or reward extinction. PMID:26763483

  9. Activation of D1/5 Dopamine Receptors: A Common Mechanism for Enhancing Extinction of Fear and Reward-Seeking Behaviors.

    Science.gov (United States)

    Abraham, Antony D; Neve, Kim A; Lattal, K Matthew

    2016-07-01

    Dopamine is critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in appetitive tasks. A parallel and growing literature indicates that dopamine signaling is involved in consolidation of memories into stable representations in aversive tasks such as fear conditioning. Relatively little is known about how dopamine may modulate memories that form during extinction, when organisms learn that the relation between previously associated events is severed. We investigated whether fear and reward extinction share common mechanisms that could be enhanced with dopamine D1/5 receptor activation. Pharmacological activation of dopamine D1/5 receptors (with SKF 81297) enhanced extinction of both cued and contextual fear. These effects also occurred in the extinction of cocaine-induced conditioned place preference, suggesting that the observed effects on extinction were not specific to a particular type of procedure (aversive or appetitive). A cAMP/PKA biased D1 agonist (SKF 83959) did not affect fear extinction, whereas a broadly efficacious D1 agonist (SKF 83822) promoted fear extinction. Together, these findings show that dopamine D1/5 receptor activation is a target for the enhancement of fear or reward extinction.

  10. Three Color Particle Optical Extinction Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design, build and test a multi-color (red, green, blue) particle optical extinction monitor suitable for use in either land or airborne applications....

  11. Epidemic extinction and control in heterogeneous networks

    CERN Document Server

    Hindes, Jason

    2016-01-01

    We consider epidemic extinction in finite networks with broad variation in local connectivity. Generalizing the theory of large fluctuations to random networks with a given degree distribution, we are able to predict the most probable, or optimal, paths to extinction in various configurations, including truncated power-laws. We find that paths for heterogeneous networks follow a limiting form in which infection first decreases in low-degree nodes, which triggers a rapid extinction in high- degree nodes, and finishes with a residual low-degree extinction. The usefulness of the approach is further demonstrated through optimal control strategies that leverage finite-size fluctuations. Interestingly, we find that the optimal control is a mix of treating both high and low-degree nodes based on large-fluctuation theoretical predictions.

  12. Protostars at Low Extinction in Orion A

    CERN Document Server

    Lewis, John Arban

    2016-01-01

    In the list of young stellar objects compiled by Megeath et al. (2012) for the Orion A molecular cloud, only 44 out of 1208 sources found projected onto low extinction (Ak<0.8 mag) gas are identified as protostars. These objects are puzzling because protostars are not typically expected to be associated with extended low extinction material. Here, we use high resolution extinction maps generated from Herschel data, optical/infrared and Spitzer Space Telescope photometry and spectroscopy of the low extinction protostellar candidate sources to determine if they are likely true protostellar sources or contaminants. Out of 44 candidate objects, we determine that 10 sources are likely protostars, with the rest being more evolved young stellar objects (18), galaxies (4), false detections of nebulosity and cloud edges (9), or real sources for which more data are required to ascertain their nature (3). We find none of the confirmed protostars to be associated with recognizable dense cores and we briefly discuss po...

  13. Are marine and nonmarine extinctions correlated?

    Science.gov (United States)

    Rampino, Michael R.

    Recent papers in Eos have debated the possible relationships between marine mass extinctions, comet showers, and volcanism [Alvarez, 1986; Officer and Grieve, 1986], and ail three might be linked [Rampino, 1987]. Moreover, as Officer and Grieve [ 1986] point out, various other causes have been suggested for given extinction events, including changes in climate, ocean circulation, and sea level fluctuations, possibly related to plate tectonics and continental positions. Also under debate is the issue of whether mass extinctions were gradual, stepped, or geologically sudden events (see, for example, Hut et al. [1987]). A missing ingredient thus far in these debates has been the record of faunal diversity of nonmarine animals. Does this show any agreement with the marine extinction record?

  14. Extinction in the Lotka-Volterra model.

    Science.gov (United States)

    Parker, Matthew; Kamenev, Alex

    2009-08-01

    Birth-death processes often exhibit an oscillatory behavior. We investigate a particular case where the oscillation cycles are marginally stable on the mean-field level. An iconic example of such a system is the Lotka-Volterra model of predator-prey interaction. Fluctuation effects due to discreteness of the populations destroy the mean-field stability and eventually drive the system toward extinction of one or both species. We show that the corresponding extinction time scales as a certain power-law of the population sizes. This behavior should be contrasted with the extinction of models stable in the mean-field approximation. In the latter case the extinction time scales exponentially with size.

  15. Biomarker Records Associated with Mass Extinction Events

    Science.gov (United States)

    Whiteside, Jessica H.; Grice, Kliti

    2016-06-01

    The history of life on Earth is punctuated by a series of mass extinction episodes that vary widely in their magnitude, duration, and cause. Biomarkers are a powerful tool for the reconstruction of historical environmental conditions and can therefore provide insights into the cause and responses to ancient extinction events. In examining the five largest mass extinctions in the geological record, investigators have used biomarkers to elucidate key processes such as eutrophy, euxinia, ocean acidification, changes in hydrological balance, and changes in atmospheric CO2. By using these molecular fossils to understand how Earth and its ecosystems have responded to unusual environmental activity during these extinctions, models can be made to predict how Earth will respond to future changes in its climate.

  16. Epidemic Extinction and Control in Heterogeneous Networks

    Science.gov (United States)

    Hindes, Jason; Schwartz, Ira B.

    2016-07-01

    We consider epidemic extinction in finite networks with a broad variation in local connectivity. Generalizing the theory of large fluctuations to random networks with a given degree distribution, we are able to predict the most probable, or optimal, paths to extinction in various configurations, including truncated power laws. We find that paths for heterogeneous networks follow a limiting form in which infection first decreases in low-degree nodes, which triggers a rapid extinction in high-degree nodes, and finishes with a residual low-degree extinction. The usefulness of our approach is further demonstrated through optimal control strategies that leverage the dependence of finite-size fluctuations on network topology. Interestingly, we find that the optimal control is a mix of treating both high- and low-degree nodes based on theoretical predictions, in contrast to methods that ignore dynamical fluctuations.

  17. Possible involvement of serotonin in extinction.

    Science.gov (United States)

    Beninger, R J; Phillips, A G

    1979-01-01

    In Experiment 1, rats were trained to leverpress for continuous reinforcement with food; half were then intubated with the serotonin synthesis inhibitor parachlorophenylalanine (PCPA: 400 mg/kg) and half with water. In extinction the PCPA-treated rats responded at a higher rate. In Experiment 2, rats were trained on a random interval schedule and then assigned to two groups, treated as in Experiment 1, and tested in extinction. There was no significant difference in the resistance to extinction of the two groups. In Experiment 3, the responding of rats trained in a punished stepdown response paradigm and then given an intragastric injection of PCPA took longer to recover than the responding of water-injected controls. These observations suggest that serotonergic neurons might play a role in extinction processes. PMID:155820

  18. Effect of coagulation on extinction in an aerosol plume propagating in the atmosphere.

    Science.gov (United States)

    Tsang, T H; Brock, J R

    1982-05-01

    Model studies based on the K-theory diffusion assumption have been carried out on aerosol plumes issuing from a crosswind line source in which advection, vertical diffusion, coagulation, sedimentation, and dry deposition are occurring. Procedures are described and a few typical results are presented. It is shown that in appropriate conditions coagulation can play an important role in altering extinction in the plume. An important coupling effect between coagulation and sedimentation/deposition has been demonstrated. In a coagulating plume it is found that total particle mass concentration cannot be inferred from measurements of extinction without a detailed consideration of the effects of coagulation. In realistic atmospheric simulations isopleths of extinction in the plume cross section show complex forms resulting from the wind gradient and its interactions with vertical diffusion and the coagulation and sedimentation/deposition processes. PMID:20389900

  19. The Impact of Accurate Extinction Measurements for X-ray Spectral Models

    CERN Document Server

    Smith, Randall K; Corrales, Lia

    2016-01-01

    Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model as a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.

  20. Quantitative analysis of forest fire extinction efficiency

    OpenAIRE

    Miguel E. Castillo-Soto; Francisco Rodríguez-Silva

    2015-01-01

    Aim of study: Evaluate the economic extinction efficiency of forest fires, based on the study of fire combat undertaken by aerial and terrestrial means. Area of study, materials and methods: Approximately 112,000 hectares in Chile. Records of 5,876 forest fires that occurred between 1998 and 2009 were analyzed. The area further provides a validation sector for results, by incorporating databases for the years 2010 and 2012. The criteria used for measuring extinction efficiency were econo...

  1. Extinction in Lotka-Volterra model

    OpenAIRE

    Parker, Matthew; Kamenev, Alex

    2009-01-01

    Competitive birth-death processes often exhibit an oscillatory behavior. We investigate a particular case where the oscillation cycles are marginally stable on the mean-field level. An iconic example of such a system is the Lotka-Volterra model of predator-prey competition. Fluctuation effects due to discreteness of the populations destroy the mean-field stability and eventually drive the system toward extinction of one or both species. We show that the corresponding extinction time scales as...

  2. Extinction Risk Escalates in the Tropics

    OpenAIRE

    Vamosi, Jana C; Steven M. Vamosi

    2008-01-01

    The latitudinal biodiversity gradient remains one of the most widely recognized yet puzzling patterns in nature [1]. Presently, the high level of extinction of tropical species, referred to as the “tropical biodiversity crisis”, has the potential to erode this pattern. While the connection between species richness, extinction, and speciation has long intrigued biologists [2], [3], these interactions have experienced increased poignancy due to their relevancy to where we should concentrate our...

  3. Tolerance of pollination networks to species extinctions.

    OpenAIRE

    Memmott, Jane; Waser, Nickolas M.; Price, Mary V.

    2004-01-01

    Mutually beneficial interactions between flowering plants and animal pollinators represent a critical 'ecosystem service' under threat of anthropogenic extinction. We explored probable patterns of extinction in two large networks of plants and flower visitors by simulating the removal of pollinators and consequent loss of the plants that depend upon them for reproduction. For each network, we removed pollinators at random, systematically from least-linked (most specialized) to most-linked (mo...

  4. Demography and the extinction of European Neanderthals

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2011-01-01

    Causes previously suggested for the sudden extinction of Neanderthals (Homo neanderthalensis) in Europe, starting around 35,000 years ago, comprise food shortage, climatic effects and violence from Modern Humans. The aim here is to formulate a demographic model with reconstructed fertility and de...... Human newcomers during the last part of the period. The conclusion is that other reasons for extinction than climate or starvation must be sought....

  5. Assessing Extinction Risk: Integrating Genetic Information

    OpenAIRE

    Gary Vinyard; Jennifer Nielsen; C. Richard Tracy; Mary Peacock; Jason Dunham

    1999-01-01

    Risks of population extinction have been estimated using a variety of methods incorporating information from different spatial and temporal scales. We briefly consider how several broad classes of extinction risk assessments, including population viability analysis, incidence functions, and ranking methods integrate information on different temporal and spatial scales. In many circumstances, data from surveys of neutral genetic variability within, and among, populations can provide informatio...

  6. Extinction rates of established spatial populations

    Science.gov (United States)

    Meerson, Baruch; Sasorov, Pavel V.

    2011-01-01

    This paper deals with extinction of an isolated population caused by intrinsic noise. We model the population dynamics in a “refuge” as a Markov process which involves births and deaths on discrete lattice sites and random migrations between neighboring sites. In extinction scenario I, the zero population size is a repelling fixed point of the on-site deterministic dynamics. In extinction scenario II, the zero population size is an attracting fixed point, corresponding to what is known in ecology as the Allee effect. Assuming a large population size, we develop a WKB (Wentzel-Kramers-Brillouin) approximation to the master equation. The resulting Hamilton’s equations encode the most probable path of the population toward extinction and the mean time to extinction. In the fast-migration limit these equations coincide, up to a canonical transformation, with those obtained, in a different way, by Elgart and Kamenev [Phys. Rev. EPHYADX1539-375510.1103/PhysRevE.70.041106 70, 041106 (2004)]. We classify possible regimes of population extinction with and without an Allee effect and for different types of refuge, and solve several examples analytically and numerically. For a very strong Allee effect, the extinction problem can be mapped into the overdamped limit of the theory of homogeneous nucleation due to Langer [Ann. Phys. (NY)APNYA60003-491610.1016/0003-4916(69)90153-5 54, 258 (1969)]. In this regime, and for very long systems, we predict an optimal refuge size that maximizes the mean time to extinction.

  7. Effect of environmental variables on body size evolution of crinoids between periods of mass extinctions

    Science.gov (United States)

    Jani, T.; Heim, N. A.; Payne, J.

    2013-12-01

    Body size plays a major role in determining whether or not an organism can sustain in its local environment. The ecosystem of an animal has a major effect on the fitness of organisms, and it would be interesting to note the degree to which various environmental factors alter body size. In my project, I identify three environmental factors that seem to affect body size of crinoids, marine invertebrates from phylum Echinodermata, and explore how these variables play out in the intervals between the five mass extinctions. The particular factors I study include atmospheric CO2 concentration (proxy for temperature), O2 concentration, and sea level. Although the r and p values for all of these factors were statistically insignificant to definitively make any correlation, there was a visual correlation. For O2, I noted a generally positive correlation with body size over time. CO2 trends suggested a negative correlation until the K-T boundary, but a positive correlation afterwards. Correlation with sea level was a little more complicated: correlation was positive from the start of the Phanerozoic to the Permian extinction; it turned negative until the Cretaceous-Tertiary boundary; afterwards, it again became positive. However, for all three variables, statistical values are too low to say definitively mark any correlation. Out of all three factors, CO2 levels had the highest correlation and lowest p-values in the most time intervals: from the start of the Phanerozoic to Ordovician-Silurian Extinction, from the Late Devonian to the Permian Extinction, and from the Cretaceous-Tertiary boundary to the present. When considering first differences, CO2 levels also had the highest correlation from the Permian Extinction to Triassic-Jurassic Extinction and from the Triassic-Jurassic Extinction to Cretaceous-Tertiary Extinction. Using PaleoTS, I found that body size evolution patterns either seemed to follow either an unbiased random walk (URW) or stasis in the intervals between

  8. How does climate change cause extinction?

    Science.gov (United States)

    Cahill, Abigail E; Aiello-Lammens, Matthew E; Fisher-Reid, M Caitlin; Hua, Xia; Karanewsky, Caitlin J; Ryu, Hae Yeong; Sbeglia, Gena C; Spagnolo, Fabrizio; Waldron, John B; Warsi, Omar; Wiens, John J

    2013-01-01

    Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.

  9. Evolution of the extinction curves in galaxies

    CERN Document Server

    Asano, Ryosuke S; Hirashita, Hiroyuki; Nozawa, Takaya

    2014-01-01

    We investigate the evolution of extinction curves in galaxies based on our evolution model of grain size distribution. In this model, we considered various processes: dust formation by SNe II and AGB stars, dust destruction by SN shocks in the ISM, metal accretion onto the surface of grains (referred to as grain growth), shattering and coagulation. We find that the extinction curve is flat in the earliest stage of galaxy evolution. As the galaxy is enriched with dust, shattering becomes effective to produce a large abundance of small grains ($a \\la 0.01\\;\\mu$m). Then, grain growth becomes effective at small grain radii, forming a bump at $a \\sim 10^{-3}${--}$10^{-2}\\;\\mu$m on the grain size distribution. Consequently, the extinction curve at ultraviolet (UV) wavelengths becomes steep, and a bump at $1/\\lambda \\sim 4.5\\;\\mu{\\rm m}^{-1}\\;(\\lambda: \\mbox{wavelength})$ on the extinction curve becomes prominent. Once coagulation becomes effective, the extinction curves become flatter, but the UV extinction remains...

  10. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    A. Nollkaemper

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  11. Compound Stimulus Extinction Reduces Spontaneous Recovery in Humans

    Science.gov (United States)

    Coelho, Cesar A. O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately…

  12. Response disinhibition may be explained as an extinction deficit in an animal model of attention-deficit/hyperactivity disorder (ADHD).

    Science.gov (United States)

    Johansen, Espen Borgå; Sagvolden, Terje

    2004-03-01

    Attention-deficit/hyperactivity disorder (ADHD) is a disorder affecting between 2 and 12% of grade-school children disturbing social, academic, and occupational functioning. Problems related to social adjustment and functioning and/or psychiatric problems will exist in 50-70% of adolescents and young adults diagnosed with ADHD as children. It has been suggested that altered reinforcement and extinction processes may cause the symptoms of ADHD. The present study investigated extinction processes in spontaneously hypertensive rats (SHR), possibly the best-validated animal model of ADHD. Extinction was tested after either a variable interval (VI) or a fixed interval (FI) schedule of reinforcement with and without the presence of a conditioned reinforcer (light in the water cubicle). The results indicate a slower extinction process in the SHR compared to the normal controls, especially during the initial transition from scheduled reinforcement to extinction. Also, more responses were retained in the SHR during the later part of extinction. The extinction deficit in the SHR may be linked to reinforcer unpredictability and the presence of conditioned reinforcers, and may explain response disinhibition seen in children with ADHD. PMID:15129781

  13. Linking Cholinergic Interneurons, Synaptic Plasticity, and Behavior during the Extinction of a Cocaine-Context Association.

    Science.gov (United States)

    Lee, Junuk; Finkelstein, Joel; Choi, Jung Yoon; Witten, Ilana B

    2016-06-01

    Despite the fact that cholinergic interneurons are a key cell type within the nucleus accumbens, a relationship between synaptic plasticity and the in vivo activity of cholinergic interneurons remains to be established. Here, we identify a three-way link between the activity of cholinergic interneurons, synaptic plasticity, and learning in mice undergoing the extinction of a cocaine-context association. We found that activity of cholinergic interneurons regulates extinction learning for a cocaine-context association and generates a sustained reduction in glutamatergic presynaptic strength onto medium spiny neurons. Interestingly, activation of cholinergic interneurons does not support reinforcement learning or plasticity by itself, suggesting that these neurons have a modulatory rather than a reinforcing function. PMID:27210555

  14. The Late Ordovician Extinction: How it became the best understood of the five major extinctions.

    Science.gov (United States)

    Sheehan, P.

    2003-04-01

    The end Ordovician extinction has become arguably the best-understood major extinction event in Earth History. A plethora of workers have established the pattern of faunal change and causes of the extinction with remarkably little disagreement. The first indication of increased extinction at the end of the Ordovician was a graph of global diversity patterns by Norman Newell in 1967, although he did not recognize it as a major event. The presence of a major extinction event became clear as William Berry and Art Boucot assembled data for Silurian correlation charts in the late 1960s. The first reports of North African glaciation in the late 1960s provided a cause for the extinction and study of the event snowballed. It was no accident that recognition of the extinction began in North America, because it was there that the extinction completely overturned faunas in the epicontinental seas. Glacio-eustatic regression of shallow seaway coincided with the disappearance of endemic Laurentian faunas and replacement by a highly cosmopolitan fauna in the Silurian. Once the event was established in North America, paleontologists soon found evidence of the event around the globe. The well-documented Hirnantia Fauna was found to correspond to the glacial interval, and Pat Brenchley soon recognized that there were two pulses of extinction, at the beginning and end of the glaciation. At the same time that the faunal changes were being documented geologic studies of the glaciation provided information on the environmental changes associated with the extinction. The timing of the glacial maximum was established in Africa and by the presence of dropstones in high latitude marine rocks. The 1990s saw geochemical techniques employed that allowed examination of atmospheric CO2 and temperature changes. In many places carbonate deposition declined. Glacio-eustatic regression was obvious in many areas, and a sea-level decline in the range of 50-100 m was established. Shallow

  15. Extinction rates in North American freshwater fishes, 1900-2010

    Science.gov (United States)

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  16. Local extinction of a coral reef fish explained by inflexible prey choice

    Science.gov (United States)

    Brooker, R. M.; Munday, P. L.; Brandl, S. J.; Jones, G. P.

    2014-12-01

    While global extinctions of marine species are infrequent, local extinctions are becoming common. However, the role of habitat degradation and resource specialisation in explaining local extinction is unknown. On coral reefs, coral bleaching is an increasingly frequent cause of coral mortality that can result in dramatic changes to coral community composition. Coral-associated fishes are often specialised on a limited suite of coral species and are therefore sensitive to these changes. This study documents the local extinction of a corallivorous reef fish, Oxymonacanthus longirostris, following a mass bleaching event that altered the species composition of associated coral communities. Local extinction only occurred on reefs that also completely lost a key prey species, Acropora millepora, even though coral cover remained high. In an experimental test, fish continued to select bleached A. millepora over the healthy, but less-preferred prey species that resisted bleaching. These results suggest that behavioural inflexibility may limit the ability of specialists to cope with even subtle changes to resource availability.

  17. Determining the extragalactic extinction law with SALT

    Science.gov (United States)

    Finkelman, Ido; Brosch, Noah; Kniazev, Alexei Y.; Buckley, David A. H.; O'Donoghue, Darragh; Hashimoto, Yas; Loaring, Nicola; Romero-Colmenero, Encarni; Still, Martin; Sefako, Ramotholo; Väisänen, Petri

    2008-11-01

    We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. The observations were performed in six spectral bands that span the spectral range from the near-ultraviolet atmospheric cut-off to the near-infrared. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11 < λ-1 < 2.94μm-1 by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. This procedure allows the derivation, with reasonably high signal-to-noise ratio, of the extinction in each spectral band we used for each resolution element of the image. We also introduce an alternative method to derive the extinction values by comparing various colour-index maps under the assumption of negligible intrinsic colour gradients in these galaxies. We than compare the results obtained using these two methods. We compare the total-to-selective extinction derived for these galaxies with previously obtained results and with similar extinction values of Milky Way dust to derive conclusions about the properties of extragalactic dust in different objects and conditions. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic environment are similar to those of the Milky Way, despite our original expectations. The ratio of the total V-band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82 +/- 0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust. We use total optical extinction values to estimate the dust mass for each galaxy, compare these with dust masses derived from IRAS measurements, and find them in the

  18. Low-Cost Avoidance Behaviors Are Resistant To Fear Extinction In Humans

    Directory of Open Access Journals (Sweden)

    Bram eVervliet

    2015-12-01

    Full Text Available Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning. Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2. Most importantly, post-extinction availaibility of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings

  19. Low-Cost Avoidance Behaviors are Resistant to Fear Extinction in Humans.

    Science.gov (United States)

    Vervliet, Bram; Indekeu, Ellen

    2015-01-01

    Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear) would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning). Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2). Most importantly, post-extinction availability of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings increased again when

  20. Low-Cost Avoidance Behaviors are Resistant to Fear Extinction in Humans.

    Science.gov (United States)

    Vervliet, Bram; Indekeu, Ellen

    2015-01-01

    Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear) would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning). Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2). Most importantly, post-extinction availability of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings increased again when

  1. Pre-synaptic control of remote fear extinction in the neocortex

    Directory of Open Access Journals (Sweden)

    Gisella eVetere

    2012-06-01

    Full Text Available Consolidation of remote memory enhances immediate early genes induction (IEGs, augments the expression of the presynaptic growth associated protein 43 (GAP-43, and increases the density and size of dendritic spines in anterior cingulate (aCC and infra-limbic (ILC cortices. Remote memory extinction, however, does not uniformly alter consolidation-induced structural changes. In the aCC, the density, but not the size, of spines is reset to pseudo-conditioning levels while novel thin spines are formed in the ILC. Whether IEGs and GAP-43 also undergo region-specific changes upon remote memory extinction is undetermined. Here we confirm in the same batch of mice that c-Fos induction and GAP-43 expression are increased in both the aCC and the ILC 36 days after contextual fear conditioning. We then show that, in both regions, remote memory extinction is associated with decrease of c-Fos induction but no change in GAP-43 expression thus revealing similar, although protein-specific, pre-synaptic adaptations in aCC and ILC neurons. These observations, in addition to our previous report of region-specific post-synaptic structural changes, disclose a complex pattern of extinction-driven neocortical alterations suitable to support erasure or reinstatement of fear according to the environment demand.

  2. Effects of hippocampal state-contingent trial presentation on hippocampus-dependent nonspatial classical conditioning and extinction.

    Science.gov (United States)

    Nokia, Miriam S; Wikgren, Jan

    2014-04-23

    Hippocampal local field potentials are characterized by two mutually exclusive states: one characterized by regular θ oscillations (∼4-8 Hz) and the other by irregular sharp-wave ripples. Presenting stimuli during dominant θ oscillations leads to expedited learning, suggesting that θ indexes a state in which encoding is most effective. However, ripple-contingent training also expedites learning, suggesting that any discrete brain state, much like the external context, can affect learning. We trained adult rabbits in trace eyeblink conditioning, a hippocampus-dependent nonspatial task, followed by extinction. Trials were delivered either in the presence or absence of θ or regardless of hippocampal state. Conditioning in the absence of θ led to more animals learning, although learning was slower compared with a yoked control group. Contrary to expectations, conditioning in the presence of θ did not affect learning. However, extinction was expedited both when it was conducted contingent on θ and when it was conducted in a state contrary to that used to trigger trials during conditioning. Strong phase-locking of hippocampal θ-band responses to the conditioned stimulus early on during conditioning predicted good learning. No such connection was observed during extinction. Our results suggest that any consistent hippocampal oscillatory state can potentially be used to regulate learning. However, the effects depend on the specific state and task at hand. Finally, much like the external environment, the ongoing neural state appears to act as a context for learning and memory retrieval.

  3. Learning

    Directory of Open Access Journals (Sweden)

    Mohsen Laabidi

    2014-01-01

    Full Text Available Nowadays learning technologies transformed educational systems with impressive progress of Information and Communication Technologies (ICT. Furthermore, when these technologies are available, affordable and accessible, they represent more than a transformation for people with disabilities. They represent real opportunities with access to an inclusive education and help to overcome the obstacles they met in classical educational systems. In this paper, we will cover basic concepts of e-accessibility, universal design and assistive technologies, with a special focus on accessible e-learning systems. Then, we will present recent research works conducted in our research Laboratory LaTICE toward the development of an accessible online learning environment for persons with disabilities from the design and specification step to the implementation. We will present, in particular, the accessible version “MoodleAcc+” of the well known e-learning platform Moodle as well as new elaborated generic models and a range of tools for authoring and evaluating accessible educational content.

  4. Conservation Risks: When Will Rhinos be Extinct?

    Science.gov (United States)

    Haas, Timothy C; Ferreira, Sam M

    2016-08-01

    We develop a risk intelligence system for biodiversity enterprises. Such enterprises depend on a supply of endangered species for their revenue. Many of these enterprises, however, cannot purchase a supply of this resource and are largely unable to secure the resource against theft in the form of poaching. Because replacements are not available once a species becomes extinct, insurance products are not available to reduce the risk exposure of these enterprises to an extinction event. For many species, the dynamics of anthropogenic impacts driven by economic as well as noneconomic values of associated wildlife products along with their ecological stressors can help meaningfully predict extinction risks. We develop an agent/individual-based economic-ecological model that captures these effects and apply it to the case of South African rhinos. Our model uses observed rhino dynamics and poaching statistics. It seeks to predict rhino extinction under the present scenario. This scenario has no legal horn trade, but allows live African rhino trade and legal hunting. Present rhino populations are small and threatened by a rising onslaught of poaching. This present scenario and associated dynamics predicts continued decline in rhino population size with accelerated extinction risks of rhinos by 2036. Our model supports the computation of extinction risks at any future time point. This capability can be used to evaluate the effectiveness of proposed conservation strategies at reducing a species' extinction risk. Models used to compute risk predictions, however, need to be statistically estimated. We point out that statistically fitting such models to observations will involve massive numbers of observations on consumer behavior and time-stamped location observations on thousands of animals. Finally, we propose Big Data algorithms to perform such estimates and to interpret the fitted model's output. PMID:26340794

  5. Elevational distribution and extinction risk in birds.

    Directory of Open Access Journals (Sweden)

    Rachel L White

    Full Text Available Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures - notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species' current elevational ranges and increased efforts to digitise and centralise such data.

  6. Effects of activation and blockade of dopamine receptors on the extinction of a passive avoidance reaction in mice with a depressive-like state.

    Science.gov (United States)

    Dubrovina, N I; Zinov'eva, D V

    2010-01-01

    Learning and extinction of a conditioned passive avoidance reaction resulting from neuropharmacological actions on dopamine D(1) and D(2) receptors were demonstrated to be specific in intact mice and in mice with a depressive-like state. Learning was degraded only after administration of the D(2) receptor antagonist sulpiride and was independent of the initial functional state of the mice. In intact mice, activation of D(2) receptors with quinpirole led to a deficit of extinction, consisting of a reduction in the ability to acquire new inhibitory learning in conditions associated with the disappearance of the expected punishment. In mice with the "behavioral despair" reaction, characterized by delayed extinction, activation of D(1) receptors with SKF38393 normalized this process, while the D(2) agonist was ineffective. A positive effect consisting of accelerated extinction of the memory of fear of the dark ("dangerous") sector of the experimental chamber was also seen on blockade of both types of dopamine receptor.

  7. Effects of activation and blockade of dopamine receptors on the extinction of a passive avoidance reaction in mice with a depressive-like state.

    Science.gov (United States)

    Dubrovina, N I; Zinov'eva, D V

    2010-01-01

    Learning and extinction of a conditioned passive avoidance reaction resulting from neuropharmacological actions on dopamine D(1) and D(2) receptors were demonstrated to be specific in intact mice and in mice with a depressive-like state. Learning was degraded only after administration of the D(2) receptor antagonist sulpiride and was independent of the initial functional state of the mice. In intact mice, activation of D(2) receptors with quinpirole led to a deficit of extinction, consisting of a reduction in the ability to acquire new inhibitory learning in conditions associated with the disappearance of the expected punishment. In mice with the "behavioral despair" reaction, characterized by delayed extinction, activation of D(1) receptors with SKF38393 normalized this process, while the D(2) agonist was ineffective. A positive effect consisting of accelerated extinction of the memory of fear of the dark ("dangerous") sector of the experimental chamber was also seen on blockade of both types of dopamine receptor. PMID:20012492

  8. Extinction of drug- and withdrawal-paired cues in animal models: relevance to the treatment of addiction.

    Science.gov (United States)

    Myers, Karyn M; Carlezon, William A

    2010-11-01

    Conditioned drug craving and withdrawal elicited by cues paired with drug use or acute withdrawal are among the many factors contributing to compulsive drug taking. Understanding how to stop these cues from having these effects is a major goal of addiction research. Extinction is a form of learning in which associations between cues and the events they predict are weakened by exposure to the cues in the absence of those events. Evidence from animal models suggests that conditioned responses to drug cues can be extinguished, although the degree to which this occurs in humans is controversial. Investigations into the neurobiological substrates of extinction of conditioned drug craving and withdrawal may facilitate the successful use of drug cue extinction within clinical contexts. While this work is still in the early stages, there are indications that extinction of drug- and withdrawal-paired cues shares neural mechanisms with extinction of conditioned fear. Using the fear extinction literature as a template, it is possible to organize the observations on drug cue extinction into a cohesive framework. PMID:20109490

  9. Quantitative analysis of forest fire extinction efficiency

    Directory of Open Access Journals (Sweden)

    Miguel E. Castillo-Soto

    2015-08-01

    Full Text Available Aim of study: Evaluate the economic extinction efficiency of forest fires, based on the study of fire combat undertaken by aerial and terrestrial means. Area of study, materials and methods: Approximately 112,000 hectares in Chile. Records of 5,876 forest fires that occurred between 1998 and 2009 were analyzed. The area further provides a validation sector for results, by incorporating databases for the years 2010 and 2012. The criteria used for measuring extinction efficiency were economic value of forestry resources, Contraction Factor analysis and definition of the extinction costs function. Main results: It is possible to establish a relationship between burnt area, extinction costs and economic losses. The method proposed may be used and adapted to other fire situations, requiring unit costs for aerial and terrestrial operations, economic value of the property to be protected and speed attributes of fire spread in free advance. Research highlights: The determination of extinction efficiency in containment works of forest fires and potential projection of losses, different types of plant fuel and local conditions favoring the spread of fire broaden the admissible ranges of a, φ and Ce considerably.

  10. Learning

    OpenAIRE

    Mohsen Laabidi; Mohamed Jemni; Leila Jemni Ben Ayed; Hejer Ben Brahim; Amal Ben Jemaa

    2014-01-01

    Nowadays learning technologies transformed educational systems with impressive progress of Information and Communication Technologies (ICT). Furthermore, when these technologies are available, affordable and accessible, they represent more than a transformation for people with disabilities. They represent real opportunities with access to an inclusive education and help to overcome the obstacles they met in classical educational systems. In this paper, we will cover basic concepts of e-access...

  11. Extinction during memory reconsolidation blocks recovery of fear in adolescents.

    Science.gov (United States)

    Johnson, D C; Casey, B J

    2015-01-01

    Adolescence is a time of intensified emotional experiences, during which anxiety and stress-related disorders peak. The most effective behavioral therapies for treating these disorders share exposure-based techniques as a core component. Exposure-based therapies build on the principles of fear extinction learning and involve desensitizing the individual to cues that trigger anxiety. Yet, recent evidence shows an adolescent-specific diminished capacity to extinguish fear responses, suggesting that adolescents may respond less well to exposure-based therapies than other age groups. Here we demonstrate an alternative method for blocking the recall of fear memories in adolescents, building on principles of memory reconsolidation in adults. During memory reconsolidation, a memory that is recalled becomes labile during which time it can be updated. Prior research has shown that extinction training during memory reconsolidation attenuates the recovery of fear memory in human adults and in rodents. Using this method, we show attenuation of fear memory in adolescent humans. These findings have significant implications for treating one of the most vulnerable populations to anxiety and stress related disorders - adolescents - by optimizing exposure therapy based on principles of memory reconsolidation. PMID:25749583

  12. Interactions of time of day and sleep with between-session habituation and extinction memory in young adult males.

    Science.gov (United States)

    Pace-Schott, Edward F; Tracy, Lauren E; Rubin, Zoe; Mollica, Adrian G; Ellenbogen, Jeffrey M; Bianchi, Matt T; Milad, Mohammed R; Pitman, Roger K; Orr, Scott P

    2014-05-01

    Within-session habituation and extinction learning co-occur as do subsequent consolidation of habituation (i.e., between-session habituation) and extinction memory. We sought to determine whether, as we predicted: (1) between-session habituation is greater across a night of sleep versus a day awake; (2) time-of-day accounts for differences; (3) between-session habituation predicts consolidation of extinction memory; (4) sleep predicts between-session habituation and/or extinction memory. Participants (N = 28) completed 4-5 sessions alternating between mornings and evenings over 3 successive days (2 nights) with session 1 in either the morning (N = 13) or evening (N = 15). Twelve participants underwent laboratory polysomnography. During 4 sessions, participants completed a loud-tone habituation protocol, while skin conductance response (SCR), blink startle electromyography (EMG), heart-rate acceleration and heart-rate deceleration (HRD) were recorded. For sessions 1 and 2, between-session habituation of EMG, SCR and HRD was greater across sleep. SCR and HRD were generally lower in the morning. Between-session habituation of SCR for sessions 1 and 2 was positively related to intervening (first night) slow wave sleep. In the evening before night 2, participants also underwent fear conditioning and extinction learning phases of a second protocol. Extinction recall was tested the following morning. Extinction recall was predicted only by between-session habituation of SCR across the same night (second night) and by intervening REM. We conclude that: (1) sleep augments between-session habituation, as does morning testing; (2) extinction recall is predicted by concurrent between-session habituation; and (3) both phenomena may be influenced by sleep. PMID:24481663

  13. Aversive Pavlovian conditioning in childhood anxiety disorders: impaired response inhibition and resistance to extinction.

    Science.gov (United States)

    Waters, Allison M; Henry, Julie; Neumann, David L

    2009-05-01

    Learning-based models of anxiety disorders emphasize the role of aversive conditioning and retarded extinction in the etiology and maintenance of anxiety disorders. Yet few studies have examined these underlying processes in children, despite that some anxiety disorders typically onset during childhood. The authors examined the acquisition and extinction of conditioned responses in 17 anxious children and 18 nonanxious control children between 8 and 12 years old using a discriminative Pavlovian conditioning procedure. One geometric shape conditional stimulus was paired with an unpleasant loud tone unconditional stimulus (CS+) whereas another geometric shape was presented alone (CS-). In the context of similar levels of discriminative conditioning in both groups, anxious children showed larger skin conductance responses to the CS+ and the CS- during acquisition and evaluated the CS+ as more arousing than the CS- compared with control children. They also showed greater resistance to extinction in skin conductance responses but not in arousal ratings to the CS+ vs. the CS- relative to control children. Results suggest that deficits in response inhibition to safety cues and retarded extinction may underlie learning processes involved in the pathogenesis of childhood anxiety disorders.

  14. Cognitive enhancers for facilitating drug cue extinction: insights from animal models.

    Science.gov (United States)

    Nic Dhonnchadha, Bríd Áine; Kantak, Kathleen M

    2011-08-01

    Given the success of cue exposure (extinction) therapy combined with a cognitive enhancer for reducing anxiety, it is anticipated that this approach will prove more efficacious than exposure therapy alone in preventing relapse in individuals with substance use disorders. Several factors may undermine the efficacy of exposure therapy for substance use disorders, but we suspect that neurocognitive impairments associated with chronic drug use are an important contributing factor. Numerous insights on these issues are gained from research using animal models of addiction. In this review, the relationship between brain sites whose learning, memory and executive functions are impaired by chronic drug use and brain sites that are important for effective drug cue extinction learning is explored first. This is followed by an overview of animal research showing improved treatment outcome for drug addiction (e.g. alcohol, amphetamine, cocaine, heroin) when explicit extinction training is conducted in combination with acute dosing of a cognitive-enhancing drug. The mechanism by which cognitive enhancers are thought to exert their benefits is by facilitating consolidation of drug cue extinction memory after activation of glutamatergic receptors. Based on the encouraging work in animals, factors that may be important for the treatment of drug addiction are considered. PMID:21295059

  15. Smectite alteration

    International Nuclear Information System (INIS)

    This report contains the proceedings of a second workshop in Washington DC December 8-9, 1983 on the alteration of smectites intended for use as buffer materials in the long-term containment of nuclear wastes. It includes extended summaries of all presentations and a transcript of the detailed scientific discussion. The discussions centered on three main questions: What is the prerequisite for and what is the precise mechanism by which smectite clays may be altered to illite. What are likly sources of potassium with respect to the KBS project. Is it likely that the conversion of smectite to illite will be of importance in the 10 5 to the 10 6 year time frame. The workshop was convened to review considerations and conclusions in connection to these questions and also to broaden the discussion to consider the use of smectite clays as buffer materials for similar applications in different geographical and geological settings. SKBF/KBS technical report 83-03 contains the proceedings from the first workshop on these matters that was held at the State University of New York, Buffalo May 26-27, 1982. (Author)

  16. Astrophysical life extinctions what killed the dinosaurs?

    CERN Document Server

    Dar, Arnon

    1999-01-01

    Geological records indicate that the exponential diversification of marine and continental life on Earth in the past 500 My was interrupted by many life extinctions. They also indicate that the major mass extinctions were correlated in time with large meteoritic impacts, gigantic volcanic eruptions, sea regressions and drastic changes in global climate. Some of these catastrophes coincided in time. The astrophysical life extinction mechanisms which were proposed so far, in particular, meteoritic impacts, nearby supernova explosions, passage through molecular or dark matter clouds, and Galactic gamma/cosmic ray bursts cannot explain the time coincidences between these catastrophes. However, recent observations suggest that many planetary-mass objects may be present in the outer solar system between the Kuiper belt and the Oort cloud. Gravitational perturbations may occasionally bring them into the inner solar system. Their passage near Earth could have generated gigantic tidal waves, large volcanic eruptions, ...

  17. Mammal extinctions, body size, and paleotemperature

    Science.gov (United States)

    Bown, T.M.; Holroyd, P.A.; Rose, K.D.

    1994-01-01

    There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

  18. Extinction in four species cyclic competition

    International Nuclear Information System (INIS)

    When four species compete stochastically in a cyclic way, the formation of two teams of mutually neutral partners is observed. In this paper we study through numerical simulations the extinction processes that can take place in this system both in the well mixed case as well as on different types of lattices. The different routes to extinction are revealed by the probability distribution of the domination time, i.e. the time needed for one team to fully occupy the system. If swapping is allowed between neutral partners, then the probability distribution is dominated by very long-lived states where a few very large domains persist, each domain being occupied by a mix of individuals from species that form one of the teams. Many aspects of the possible extinction scenarios are lost when only considering averaged quantities, such as for example the mean domination time. (paper)

  19. Life extinctions by neutron star mergers

    CERN Document Server

    Dar, Arnon; Shaviv, N J; Dar, Arnon; Laor, Ari; Shaviv, Nir J.

    1997-01-01

    High energy cosmic ray jets from nearby mergers or accretion induced collapse (AIC) of neutron stars (NS) that hit the atmosphere can produce lethal fluxes of atmospheric muons at ground level, underground and underwater, destroy the ozone layer and radioactivate the environment. They could have caused most of the massive life extinctions on planet Earth in the past 600 My. Biological mutations due to ionizing radiations could have caused the fast appearance of new species after the massive extinctions. An early warning of future extinctions due to NS mergers may be obtained by identifying, mapping and timing all the nearby binary neutron stars systems. A warning of an approaching cosmic ray burst from a nearby NS merger/AIC may be provided by a very intense gamma ray burst which preceeds it.

  20. Does supplementary reinforcement of stereotypy facilitate extinction?

    Science.gov (United States)

    Dozier, Claudia L; Iwata, Brian A; Wilson, David M; Thomason-Sassi, Jessica L; Roscoe, Eileen M

    2013-01-01

    Results of several studies suggest that delivery of supplemental (social) reinforcement for stereotypy might facilitate its subsequent extinction. We examined this possibility with 9 subjects who engaged in stereotypy by including methodological refinements to ensure that (a) subjects' stereotypy was maintained in the absence of social consequences, (b) supplementary reinforcers were highly preferred and were shown to be reinforcers for some behavior, and (c) subjects were exposed to lengthy reinforcement and extinction conditions. In spite of these modifications, only 4 subjects' stereotypy increased when supplementary reinforcement was delivered contingent on stereotypy, and no subject's stereotypy decreased below initial baseline levels when social reinforcement was subsequently withheld. Decreases in stereotypy occurred with the implementation of noncontingent reinforcement. Thus, delivery of supplementary reinforcers either did not increase stereotypy or did not facilitate extinction of stereotypy maintained by automatic reinforcement. We discuss the practical and conceptual bases of these results with respect to our current understanding of function-based interventions.

  1. Extinction rate fragility in population dynamics.

    Science.gov (United States)

    Khasin, M; Dykman, M I

    2009-08-01

    Population extinction is of central interest for population dynamics. It may occur from a large rare fluctuation. We find that, in contrast to related large-fluctuation effects like noise-induced interstate switching, quite generally extinction rates in multipopulation systems display fragility, where the height of the effective barrier to be overcome in the fluctuation depends on the system parameters nonanalytically. We show that one of the best-known models of epidemiology, the susceptible-infectious-susceptible model, is fragile to total population fluctuations.

  2. Micro-evolutionary diversification among Indian Ocean parrots: temporal and spatial changes in phylogenetic diversity as a consequence of extinction and invasion

    OpenAIRE

    Jackson, H.; Jones, C G; Agapow, P-M; Tatayah, V; Groombridge, Jim J

    2015-01-01

    Almost 90% of global bird extinctions have occurred on islands. The loss of endemic spe- cies from island systems can dramatically alter evolutionary trajectories of insular species biodiversity, resulting in a loss of evolutionary diversity important for species adaptation to changing environments. The Western Indian Ocean islands have been the scene of evolution for a large number of endemic parrots. Since their discovery in the 16th cen- tury, many of these parrots have become extinct or h...

  3. Dexamethasone Treatment Leads to Enhanced Fear Extinction and Dynamic Fkbp5 Regulation in Amygdala.

    Science.gov (United States)

    Sawamura, Takehito; Klengel, Torsten; Armario, Antonio; Jovanovic, Tanja; Norrholm, Seth D; Ressler, Kerry J; Andero, Raül

    2016-02-01

    Posttraumatic stress disorder (PTSD) is both a prevalent and debilitating trauma-related disorder associated with dysregulated fear learning at the core of many of its signs and symptoms. Improvements in the currently available psychological and pharmacological treatments are needed in order to improve PTSD treatment outcomes and to prevent symptom relapse. In the present study, we used a putative animal model of PTSD that included presentation of immobilization stress (IMO) followed by fear conditioning (FC) a week later. We then investigated the acute effects of GR receptor activation on the extinction (EXT) of conditioned freezing, using dexamethasone administered systemically which is known to result in suppression of the HPA axis. In our previous work, IMO followed by tone-shock-mediated FC was associated with impaired fear EXT. In this study, we administered dexamethasone 4 h before EXT training and then examined EXT retention (RET) 24 h later to determine whether dexamethasone suppression rescued EXT deficits. Dexamethasone treatment produced dose-dependent enhancement of both EXT and RET. Dexamethasone was also associated with reduced amygdala Fkbp5 mRNA expression following EXT and after RET. Moreover, DNA methylation of the Fkbp5 gene occurred in a dose-dependent and time course-dependent manner within the amygdala. Additionally, we found dynamic changes in epigenetic regulation, including Dnmt and Tet gene pathways, as a function of both fear EXT and dexamethasone suppression of the HPA axis. Together, these data suggest that dexamethasone may serve to enhance EXT by altering Fkbp5-mediated glucocorticoid sensitivity via epigenetic regulation of Fkbp5 expression.

  4. Confounding environmental colour and distribution shape leads to underestimation of population extinction risk.

    Directory of Open Access Journals (Sweden)

    Mike S Fowler

    Full Text Available The colour of environmental variability influences the size of population fluctuations when filtered through density dependent dynamics, driving extinction risk through dynamical resonance. Slow fluctuations (low frequencies dominate in red environments, rapid fluctuations (high frequencies in blue environments and white environments are purely random (no frequencies dominate. Two methods are commonly employed to generate the coloured spatial and/or temporal stochastic (environmental series used in combination with population (dynamical feedback models: autoregressive [AR(1] and sinusoidal (1/f models. We show that changing environmental colour from white to red with 1/f models, and from white to red or blue with AR(1 models, generates coloured environmental series that are not normally distributed at finite time-scales, potentially confounding comparison with normally distributed white noise models. Increasing variability of sample Skewness and Kurtosis and decreasing mean Kurtosis of these series alter the frequency distribution shape of the realised values of the coloured stochastic processes. These changes in distribution shape alter patterns in the probability of single and series of extreme conditions. We show that the reduced extinction risk for undercompensating (slow growing populations in red environments previously predicted with traditional 1/f methods is an artefact of changes in the distribution shapes of the environmental series. This is demonstrated by comparison with coloured series controlled to be normally distributed using spectral mimicry. Changes in the distribution shape that arise using traditional methods lead to underestimation of extinction risk in normally distributed, red 1/f environments. AR(1 methods also underestimate extinction risks in traditionally generated red environments. This work synthesises previous results and provides further insight into the processes driving extinction risk in model populations. We

  5. Modern 'junk food' and minimally-processed 'natural food' cafeteria diets alter the response to sweet taste but do not impair flavor-nutrient learning in rats.

    Science.gov (United States)

    Palframan, Kristen M; Myers, Kevin P

    2016-04-01

    Animals learn to prefer and increase consumption of flavors paired with postingestive nutrient sensing. Analogous effects have been difficult to observe in human studies. One possibility is experience with the modern, processed diet impairs learning. Food processing manipulates flavor, texture, sweetness, and nutrition, obscuring ordinary correspondences between sensory cues and postingestive consequences. Over time, a diet of these processed 'junk' foods may impair flavor-nutrient learning. This 'flavor-confusion' hypothesis was tested by providing rats long-term exposure to cafeteria diets of unusual breadth (2 or 3 foods per day, 96 different foods over 3 months, plus ad libitum chow). One group was fed processed foods (PF) with added sugars/fats and manipulated flavors, to mimic the sensory-nutrient properties of the modern processed diet. Another group was fed only 'natural' foods (NF) meaning minimally-processed foods without manipulated flavors or added sugars/fats (e.g., fresh fruits, vegetables, whole grains) ostensibly preserving the ordinary correspondence between flavors and nutrition. A CON group was fed chow only. In subsequent tests of flavor-nutrient learning, PF and NF rats consistently acquired strong preferences for novel nutrient-paired flavors and PF rats exhibited enhanced learned acceptance, contradicting the 'flavor-confusion' hypothesis. An unexpected finding was PF and NF diets both caused lasting reduction in ad lib sweet solution intake. Groups did not differ in reinforcing value of sugar in a progressive ratio task. In lick microstructure analysis the NF group paradoxically showed increased sucrose palatability relative to PF and CON, suggesting the diets have different effects on sweet taste evaluation.

  6. Attentional, Associative, and Configural Mechanisms in Extinction

    Science.gov (United States)

    Larrauri, Jose A.; Schmajuk, Nestor A.

    2008-01-01

    The participation of attentional and associative mechanisms in extinction, spontaneous recovery, external disinhibition, renewal, reinstatement, and reacquisition was evaluated through computer simulations with an extant computational model of classical conditioning (N. A. Schmajuk, Y. Lam, & J. A. Gray, 1996; N. A. Schmajuk & J. A. Larrauri,…

  7. Optical atmospheric extinction over Cerro Paranal

    CERN Document Server

    Patat, F; O'Brien, K; Pompei, E; Bensby, T; Carraro, G; Postigo, A de Ugarte; Fox, A; Gavignaud, I; James, G; Korhonen, H; Ledoux, C; Randall, S; Sana, H; Smoker, J; Stefl, S; Szeifert, T

    2010-01-01

    Aims: The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with an accuracy of 0.01 mag/airmass. Methods: The extinction curve of Paranal was obtained through low-resolution spectroscopy of 8 spectrophotometric standard stars observed with FORS1 mounted at the 8.2 m Very Large Telescope, covering a spectral range 3300-8000 A. A total of 600 spectra were collected on more than 40 nights distributed over six months, from October 2008 to March 2009. The average extinction curve was derived using a global fit algorithm, which allowed us to simultaneously combine all the available data. The main atmospheric parameters were retrieved using the LBLRTM radiative transfer code, which was also utilised to study the impact of variability of the main molecular bands of O2, O3, and H2O, and to estimate their column densities. Results: In general, the extinction curve of Paranal appears to conform to those derived for other astronomical si...

  8. The extinction of inflection in Old English

    OpenAIRE

    FOMENKO LARISA NIKOLAYEVNA

    2016-01-01

    This article shows the process of extinction of inflections in the flexion Old English, which accelerated due to related languages of the invaders and the Anglo-Saxon, contributed to the confusion of these languages. As a result, such grammatical consequences in the field of morphology.

  9. Development of the mediterranean extinction code (MEDEX)

    NARCIS (Netherlands)

    Piazzola, J.; Bouchara, F.; Leeuw, G. de; Eijk, A.M.J. van

    2003-01-01

    The performance of electro-optical systems can be substantially affected by aerosol particles that scatter and absorb electromagnetic radiation. The model that is most frequently used for the prediction of aerosols and their effect on extinction in the marine atmosphere is the US Navy Aerosol Model

  10. Optical atmospheric extinction over Cerro Paranal

    NARCIS (Netherlands)

    F. Patat; S. Moehler; K. O'Brien; E. Pompei; T. Bensby; G. Carraro; A. de Ugarte Postigo; A. Fox; I. Gavignaud; G. James; H. Korhonen; C. Ledoux; S. Randall; H.A.A. Sana; J. Smoker; S. Stefl; T. Szeifert

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass-1. Additionally

  11. Future Student Support Programs: Distinction or Extinction?

    Science.gov (United States)

    Johnson, Sharon K.; Johnson, C. D.

    This chapter reviews changes for the future of student support programs identified and addressed by other contributing authors. It is proposed that without a blueprint of how the fields of school counseling, psychology, nursing, social work, and other student support programs will change to address the future, extinction is guaranteed. Changes…

  12. Recent animal extinctions: Recipes for disaster

    Energy Technology Data Exchange (ETDEWEB)

    Burnery, D.A. (Fordham Univ., Bronx, NY (United States))

    Many late-prehistoric extinctions share ingredients: climate and vegetation change, human hunting, and the arrival of exotic animals. This article looks at evidence from the past to compare with the concerns about biodiversity in the present. For example, thousands of years ago North America rivaled Africa's Serengeti Plains for big animals. Almost all disappeared from the fossil record 11,000 years ago at approximately the same time as evidence for human beings and rapid climate change also appear in the fossil record. Topics discussed in the article include the following: evidence from Euroasian art; the remarkable large-animal extinctions which occured in Australia and New Guinea by the end of the last ice age; the Blitzcrieg Hypotheses involving the early American big-game hunters overkill (contribution of climate change and other human activities and the lack of similar south American evidence included); late Pleistocene extinction on isolated oceanic islands, including evidence of human/animal interaction; Hawaii, New Zealand, Madagascar; lessons from this past reconstruction of extinctions. 12 refs., 17 figs.

  13. Hibernation and daily torpor minimize mammalian extinctions

    Science.gov (United States)

    Geiser, Fritz; Turbill, Christopher

    2009-10-01

    Small mammals appear to be less vulnerable to extinction than large species, but the underlying reasons are poorly understood. Here, we provide evidence that almost all (93.5%) of 61 recently extinct mammal species were homeothermic, maintaining a constant high body temperature and thus energy expenditure, which demands a high intake of food, long foraging times, and thus exposure to predators. In contrast, only 6.5% of extinct mammals were likely heterothermic and employed multi-day torpor (hibernation) or daily torpor, even though torpor is widespread within more than half of all mammalian orders. Torpor is characterized by substantial reductions of body temperature and energy expenditure and enhances survival during adverse conditions by minimizing food and water requirements, and consequently reduces foraging requirements and exposure to predators. Moreover, because life span is generally longer in heterothermic mammals than in related homeotherms, heterotherms can employ a ‘sit-and-wait’ strategy to withstand adverse periods and then repopulate when circumstances improve. Thus, torpor is a crucial but hitherto unappreciated attribute of small mammals for avoiding extinction. Many opportunistic heterothermic species, because of their plastic energetic requirements, may also stand a better chance of future survival than homeothermic species in the face of greater climatic extremes and changes in environmental conditions caused by global warming.

  14. Methylphenidate Enhances Extinction of Contextual Fear

    Science.gov (United States)

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show…

  15. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the ex

  16. Modulation of Fear Extinction by Stress, Stress Hormones and Estradiol: A Review

    OpenAIRE

    Stockhorst, Ursula; Antov, Martin I.

    2016-01-01

    Fear acquisition and extinction are valid models for the etiology and treatment of anxiety, trauma- and stressor-related disorders. These disorders are assumed to involve aversive learning under acute and/or chronic stress. Importantly, fear conditioning and stress share common neuronal circuits. The stress response involves multiple changes interacting in a time-dependent manner: (a) the fast first-wave stress response [with central actions of noradrenaline, dopamine, serotonin, corticotropi...

  17. Fear Extinction as a Model for Synaptic Plasticity in Major Depressive Disorder

    OpenAIRE

    Marion Kuhn; Nora Höger; Bernd Feige; Jens Blechert; Claus Normann; Christoph Nissen

    2014-01-01

    BACKGROUND: The neuroplasticity hypothesis of major depressive disorder proposes that a dysfunction of synaptic plasticity represents a basic pathomechanism of the disorder. Animal models of depression indicate enhanced plasticity in a ventral emotional network, comprising the amygdala. Here, we investigated fear extinction learning as a non-invasive probe for amygdala-dependent synaptic plasticity in patients with major depressive disorder and healthy controls. METHODS: Differential fear con...

  18. Modulation of fear extinction by stress, stress hormones and estradiol: a review

    OpenAIRE

    Ursula eStockhorst; Antov, Martin I.

    2016-01-01

    Fear acquisition and extinction are valid models for the etiology and treatment of anxiety, trauma- and stressor-related disorders. These disorders are assumed to involve aversive learning under acute and/or chronic stress. Importantly, fear conditioning and stress share common neuronal circuits. The stress response involves multiple changes interacting in a time-dependent manner: (a) the fast first-wave stress response (with central actions of noradrenaline, dopamine, serotonin, corticotropi...

  19. Fear conditioning and extinction across development: Evidence from human studies and animal models☆

    OpenAIRE

    Shechner, Tomer; Hong, Melanie; Britton, Jennifer C.; Pine, Daniel S.; Fox, Nathan A.

    2014-01-01

    The ability to differentiate danger and safety through associative processes emerges early in life. Understanding the mechanisms underlying associative learning of threat and safety can clarify the processes that shape development of normative fears and pathological anxiety. Considerable research has used fear conditioning and extinction paradigms to delineate underlying mechanisms in animals and human adults; however, little is known about these mechanisms in children and adolescents. The cu...

  20. A REMARK ON EXTINCTION OF A CLASS OF SUPERPROCESSES

    Institute of Scientific and Technical Information of China (English)

    ZHAOXUELEI

    1996-01-01

    The extinction of a class of superprocesses associated with general branching characteristics and underlying Markov processes is investigted, The extinction is closely associated with the branching characteristics and the recurrence and transience of underlying processes.

  1. Modeling the Infrared Extinction toward the Galactic Center

    CERN Document Server

    Gao, Jian; Jiang, B W

    2013-01-01

    We model the ~1--19$\\mum$ infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be Av~38--42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep ~1--3$\\mum$ near-IR extinction and the flat ~3--8$\\mum$ mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small Rv and steep near-IR extinction), and dust in dense regions (characterized by large Rv and flat UV extinction).

  2. Preservation of Natural Diversity: The Problem of Extinction Prone Species

    Science.gov (United States)

    Terborgh, John

    1974-01-01

    Examines threatened extinction of birds and recommends agencies adopt policies which minimize the pace of extinctions through the setting aside of large preserves which protect natural vegetation formation and the animal life. (BR)

  3. Effect of Dust Extinction on Gamma-ray Burst Afterglows

    Science.gov (United States)

    Lŭ, Gu-Jing; Shao, Lang; Jin, Zhi-Ping; Wei, Da-Ming

    2011-10-01

    In order to study the effect of dust extinction on the afterglow of gamma-ray bursts (GRBs), we carry out numerical calculations with high precision based on the rigorous Mie theory and the latest optical properties of interstellar dust grains, and analyze the different extinction curves produced by dust grains with different physical parameters. Our results indicate that the absolute extinction quantity is substantially determined by the medium density and metallicity. However, the shape of the extinction curve is mainly determined by the size distribution of the dust grains. If the dust grains aggregate to form larger ones, they will cause a flatter or grayer extinction curve with lower extinction quantity. On the contrary, if the dust grains are disassociated to smaller ones due to some uncertain processes, they will cause a steeper extinction curve with larger amount of extinction. These results might provide an important insight into understanding the origin of the optically dark GRBs.

  4. Effect of Dust Extinction on Gamma-ray Burst Afterglows

    CERN Document Server

    Lv, Gu-Jing; Jin, Zhi-Ping; Wei, Da-Ming

    2011-01-01

    In order to study the effect of dust extinction on the afterglow of gamma-ray bursts (GRBs), we carry out numerical calculations with high precision based on rigorous Mie theory and latest optical properties of interstellar dust grains, and analyze the different extinction curves produced by dust grains with different physical parameters. Our results indicate that the absolute extinction quantity is substantially determined by the medium density and metallicity. However, the shape of the extinction curve is mainly determined by the size distribution of the dust grains. If the dust grains aggregate to form larger ones, they will cause a flatter or grayer extinction curve with lower extinction quantity. On the contrary, if the dust grains are disassociated to smaller ones due to some uncertain processes, they will cause a steeper extinction curve with larger amount of extinction. These results might provide an important insight into understanding the origin of the optically dark GRBs.

  5. Modulation of fear extinction by stress, stress hormones and estradiol: a review

    Directory of Open Access Journals (Sweden)

    Ursula eStockhorst

    2016-01-01

    Full Text Available Fear acquisition and extinction are valid models for the etiology and treatment of anxiety, trauma- and stressor-related disorders. These disorders are assumed to involve aversive learning under acute and/or chronic stress. Importantly, fear conditioning and stress share common neuronal circuits. The stress response involves multiple changes interacting in a time-dependent manner: (a the fast first-wave stress response (with central actions of noradrenaline, dopamine, serotonin, corticotropin-releasing hormone, plus increased sympathetic tone and peripheral catecholamine release and (b the second-wave stress response (with peripheral release of glucocorticoids after activation of the hypothalamus-pituitary-adrenocortical axis. Control of fear during extinction is also sensitive to these stress-response mediators. In the present review, we will thus examine current animal and human data, addressing the role of stress and single stress-response mediators for successful acquisition, consolidation and recall of fear extinction. We report studies using pharmacological manipulations targeting a number of stress-related neurotransmitters and neuromodulators (monoamines, opioids, endocannabinoids, neuropeptide Y, oxytocin, glucocorticoids and behavioral stress induction. As anxiety, trauma- and stressor-related disorders are more common in women, recent research focuses on female sex hormones and identifies a potential role for estradiol in fear extinction. We will thus summarize animal and human data on the role of estradiol and explore possible interactions with stress or stress-response mediators in extinction. This also aims at identifying time-windows of enhanced (or reduced sensitivity for fear extinction, and thus also for successful exposure therapy.

  6. Modulation of Fear Extinction by Stress, Stress Hormones and Estradiol: A Review

    Science.gov (United States)

    Stockhorst, Ursula; Antov, Martin I.

    2016-01-01

    Fear acquisition and extinction are valid models for the etiology and treatment of anxiety, trauma- and stressor-related disorders. These disorders are assumed to involve aversive learning under acute and/or chronic stress. Importantly, fear conditioning and stress share common neuronal circuits. The stress response involves multiple changes interacting in a time-dependent manner: (a) the fast first-wave stress response [with central actions of noradrenaline, dopamine, serotonin, corticotropin-releasing hormone (CRH), plus increased sympathetic tone and peripheral catecholamine release] and (b) the second-wave stress response [with peripheral release of glucocorticoids (GCs) after activation of the hypothalamus-pituitary-adrenocortical (HPA) axis]. Control of fear during extinction is also sensitive to these stress-response mediators. In the present review, we will thus examine current animal and human data, addressing the role of stress and single stress-response mediators for successful acquisition, consolidation and recall of fear extinction. We report studies using pharmacological manipulations targeting a number of stress-related neurotransmitters and neuromodulators [monoamines, opioids, endocannabinoids (eCBs), neuropeptide Y, oxytocin, GCs] and behavioral stress induction. As anxiety, trauma- and stressor-related disorders are more common in women, recent research focuses on female sex hormones and identifies a potential role for estradiol in fear extinction. We will thus summarize animal and human data on the role of estradiol and explore possible interactions with stress or stress-response mediators in extinction. This also aims at identifying time-windows of enhanced (or reduced) sensitivity for fear extinction, and thus also for successful exposure therapy. PMID:26858616

  7. Toward an animal model of extinction-induced despair: focus on aging and physiological indices.

    Science.gov (United States)

    Huston, Joseph P; Schulz, Daniela; Topic, Bianca

    2009-08-01

    Behaviors that are under the control of positive or negative reinforcers undergo extinction when the anticipated reward/reinforcer is withheld. Despair, an important symptom of environmentally determined depression in humans, can be generated by extinction, or the failure of expected reward to accrue. Although well known to clinicians dealing with depressive patients, an animal model has not been available for extinction-induced depression. We have made a beginning towards validating such a model, based on the extinction of negatively reinforced behavior in the rat, i.e., upon removal of the possibility to escape onto a safety platform in the water maze. As a marker for despair, we employed behavioral immobility, i.e., the cessation of swimming in the attempt to find safety from the water, presumably, a type of learned helplessness. This measure was sensitive to antidepressants and correlated with neurotransmitter contents, neurotrophins and hypothalamus-pituitary adrenal axis markers in selected sites of the brain. Given that some cases of depression in the elderly may be biologically distinct from others and from early-onset depression, and since particularly the aged are prone to experience extinction-induced despair, we compared aged (ca. 24 months old) animals with adults in most of our studies. We found a number of distinct differences in behavioral and biological measures, indicative of differences in propensity to, as well as response to, extinction-induced despair between aged and adults. Our results add to the body of evidence for differences in the neurobiological substrates of depressive disorders between aged and adults, with the implication for the requirement of different treatment strategies in these two populations. PMID:19350220

  8. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

    DEFF Research Database (Denmark)

    Finnegan, Seth; Mac Ørum Rasmussen, Christian; Harper, David A. T.

    2016-01-01

    The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician...... in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions...... between shifting climate zones and palaeobiogeography may also have been important. We test the latter hypothesis by estimating whether each genus would have been able to track habitats within its thermal tolerance range during the greenhouse–icehouse climate transition. Models including these estimates...

  9. Animal learning.

    Science.gov (United States)

    Castro, Leyre; Wasserman, Edward A

    2010-01-01

    Pavlov and Thorndike pioneered the experimental study of animal learning and provided psychologists with powerful tools to unveil its underlying mechanisms. Today's research developments and theoretical analyses owe much to the pioneering work of these early investigators. Nevertheless, in the evolution of our knowledge about animal learning, some initial conceptions have been challenged and revised. We first review the original experimental procedures and findings of Pavlov and Thorndike. Next, we discuss critical research and consequent controversies which have greatly shaped animal learning theory. For example, although contiguity seemed to be the only condition that is necessary for learning, we now know that it is not sufficient; the conditioned stimulus (CS) also has to provide information about the occurrence of the unconditioned stimulus (US). Also, animals appear to learn different things about the same stimuli when circumstances vary. For instance, when faced with situations in which the meaning of a CS changes, as in the case of acquisition and later extinction, animals seem to preserve the original knowledge (CS-US) in addition to learning about the new conditions (CS-noUS). Finally, we discuss how parallels among Pavlovian conditioning, operant conditioning, and human causal judgment suggest that causal knowledge may lie at the root of both human and animal learning. All of these empirical findings and theoretical developments prove that animal learning is more complex and intricate than was once imagined. Copyright © 2009 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website. PMID:26272842

  10. Dopamine and extinction: a convergence of theory with fear and reward circuitry.

    Science.gov (United States)

    Abraham, Antony D; Neve, Kim A; Lattal, K Matthew

    2014-02-01

    Research on dopamine lies at the intersection of sophisticated theoretical and neurobiological approaches to learning and memory. Dopamine has been shown to be critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in reward-related tasks. A parallel and growing literature indicates that dopamine is involved in fear conditioning and extinction. These studies are consistent with long-standing ideas about appetitive-aversive interactions in learning theory and they speak to the general nature of cellular and molecular processes that underlie behavior. We review the behavioral and neurobiological literature showing a role for dopamine in fear conditioning and extinction. At a cellular level, we review dopamine signaling and receptor pharmacology, cellular and molecular events that follow dopamine receptor activation, and brain systems in which dopamine functions. At a behavioral level, we describe theories of learning and dopamine function that could describe the fundamental rules underlying how dopamine modulates different aspects of learning and memory processes.

  11. Dopamine and extinction: a convergence of theory with fear and reward circuitry.

    Science.gov (United States)

    Abraham, Antony D; Neve, Kim A; Lattal, K Matthew

    2014-02-01

    Research on dopamine lies at the intersection of sophisticated theoretical and neurobiological approaches to learning and memory. Dopamine has been shown to be critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in reward-related tasks. A parallel and growing literature indicates that dopamine is involved in fear conditioning and extinction. These studies are consistent with long-standing ideas about appetitive-aversive interactions in learning theory and they speak to the general nature of cellular and molecular processes that underlie behavior. We review the behavioral and neurobiological literature showing a role for dopamine in fear conditioning and extinction. At a cellular level, we review dopamine signaling and receptor pharmacology, cellular and molecular events that follow dopamine receptor activation, and brain systems in which dopamine functions. At a behavioral level, we describe theories of learning and dopamine function that could describe the fundamental rules underlying how dopamine modulates different aspects of learning and memory processes. PMID:24269353

  12. Extinction and reinstatement to cocaine-associated cues in male and female juvenile rats and the role of D1 dopamine receptor.

    Science.gov (United States)

    Brenhouse, Heather C; Thompson, Britta S; Sonntag, Kai C; Andersen, Susan L

    2015-08-01

    Extinction of behaviors in response to drug-associated cues and prevention of reinstatement are integral for addiction treatment, and can reverse or ameliorate the harmful consequences of drug use. The mechanisms controlling extinction and reinstatement involve prefrontal cortical dopamine receptors, which change in expression and activity during the juvenile and adolescent transitions until they mature in adulthood. Little is known about the role that PFC D1 dopamine receptors play in extinction of drug-paired associations early in life. We used extinction of place preferences for cocaine in juvenile male and female rats following genetic, cell-specific overexpression of D1 on glutamatergic cells in the PFC. All subjects needed to demonstrate cocaine preferences for inclusion in the extinction studies. Here, male juveniles with a preference to 10 mg/kg cocaine took longer to extinguish preferences compared to both male adults and female juveniles. Female juveniles extinguished more rapidly than male juveniles at 20 mg/kg cocaine. Overexpression of D1 in juvenile males significantly facilitated extinction relative to juvenile male controls, whereas D1 prolonged expression of extinction in adults overexpressing D1 and adolescents who naturally have elevated D1 expression. These data suggest that an immature D1 profile in juveniles prevented the learning of new associations, and D1 overexpression may provide sufficient activity to facilitate extinction learning. D1 overexpression reduced reinstatement to a priming dose of cocaine in juvenile males. Together, these data show D1 expression may re-program motivational circuitry to facilitate extinction learning during juvenility that is normally unavailable to juveniles and that sex differences exist. PMID:25749358

  13. Exposure to music in the perinatal period enhances learning performance and alters BDNF/TrkB signaling in mice as adults.

    Science.gov (United States)

    Chikahisa, Sachiko; Sei, Hiroyoshi; Morishima, Masaki; Sano, Atsuko; Kitaoka, Kazuyoshi; Nakaya, Yutaka; Morita, Yusuke

    2006-05-15

    Music has been suggested to have a beneficial effect on various types of performance in humans. However, the physiological and molecular mechanism of this effect remains unclear. We examined the effect of music exposure during the perinatal period on learning behavior in adult mice, and measured the levels of brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase receptor B (TrkB), which play critical roles in synaptic plasticity. In addition, we measured the levels of 3-phosphoinositide-dependent protein kinase-1 (PDK1) and mitogen-activated protein kinase (MAPK), downstream targets of two main pathways in BDNF/TrkB signaling. Music-exposed mice completed a maze learning task with fewer errors than the white noise-exposed mice and had lower levels of BDNF and higher levels of TrkB and PDK1 in the cortex. MAPK levels were unchanged. Furthermore, TrkB and PDK1 protein levels in the cortex showed a significant negative correlation with the number of errors on the maze. These results suggest that perinatal exposure of mice to music has an influence on BDNF/TrkB signaling and its intracellular signaling pathway targets, including PDK1, and thus may induce improved learning and memory functions.

  14. Alien species as a driver of recent extinctions.

    Science.gov (United States)

    Bellard, Céline; Cassey, Phillip; Blackburn, Tim M

    2016-02-01

    We assessed the prevalence of alien species as a driver of recent extinctions in five major taxa (plants, amphibians, reptiles, birds and mammals), using data from the IUCN Red List. Our results show that alien species are the second most common threat associated with species that have gone completely extinct from these taxa since AD 1500. Aliens are the most common threat associated with extinctions in three of the five taxa analysed, and for vertebrate extinctions overall. PMID:26888913

  15. Geography of end-Cretaceous marine bivalve extinctions

    Science.gov (United States)

    Raup, David M.; Jablonski, David

    1993-01-01

    Analysis of the end-Cretaceous mass extinction, based on 3514 occurrences of 340 genera of marine bivalves (Mollusca), suggests that extinction intensities were uniformly global; no latitudinal gradients or other geographic patterns are detected. Elevated extinction intensities in some tropical areas are entirely a result of the distribution of one extinct group of highly specialized bivalves, the rudists. When rudists are omitted, intensities at those localities are statistically indistinguishable from those of both the rudist-free tropics and extratropical localities.

  16. Endangered Species and Natural Resource Exploitation: Extinction vs. Coexistence

    OpenAIRE

    Tsur, Yacov; Zemel, Amos

    1994-01-01

    The threat on the survival of animal species due to intensive use of natural resources is incorporated within resource management models, paying special attention to uncertainty regarding the conditions that lead to extinction. The manner in which the potential benefits forgone due to the species extinction (denoted extinction penalty) induce more conservative exploitation policies is studied in detail. When the extinction penalty is ignored, the optimal policy is to drive the resource stock ...

  17. Prefrontal inputs to the amygdala instruct fear extinction memory formation

    OpenAIRE

    Bukalo, Olena; Pinard, Courtney R.; Silverstein, Shana; Brehm, Christina; Hartley, Nolan D.; Whittle, Nigel; Colacicco, Giovanni; Busch, Erica; Patel, Sachin; Singewald, Nicolas; Holmes, Andrew

    2015-01-01

    Persistent anxiety after a psychological trauma is a hallmark of many anxiety disorders. However, the neural circuits mediating the extinction of traumatic fear memories remain incompletely understood. We show that selective, in vivo stimulation of the ventromedial prefrontal cortex (vmPFC)–amygdala pathway facilitated extinction memory formation, but not retrieval. Conversely, silencing the vmPFC-amygdala pathway impaired extinction formation and reduced extinction-induced amygdala activity....

  18. The L-Type Calcium Channel Blocker Nifedipine Impairs Extinction, but Not Reduced Contingency Effects, in Mice

    Science.gov (United States)

    Jami, Shekib; Barad, Mark; Cain, Christopher K.; Godsil, Bill P.

    2005-01-01

    We recently reported that fear extinction, a form of inhibitory learning, is selectively blocked by systemic administration of L-type voltage-gated calcium channel (LVGCC) antagonists, including nifedipine, in mice. We here replicate this finding and examine three reduced contingency effects after vehicle or nifedipine (40 mg/kg) administration.…

  19. Hippocampal Erk Mechanisms Linking Prediction Error to Fear Extinction: Roles of Shock Expectancy and Contextual Aversive Valence

    Science.gov (United States)

    Huh, Kyu Hwan; Guzman, Yomayra F.; Tronson, Natalie C.; Guedea, Anita L.; Gao, Can; Radulovic, Jelena

    2009-01-01

    Extinction of fear requires learning that anticipated aversive events no longer occur. Animal models reveal that sustained phosphorylation of the extracellular signal-regulated kinase (Erk) in hippocampal CA1 neurons plays an important role in this process. However, the key signals triggering and regulating the activity of Erk are not known. By…

  20. Gradual extinction prevents the return of fear: Implications for the discovery of state

    Directory of Open Access Journals (Sweden)

    Samuel Joseph Gershman

    2013-11-01

    Full Text Available Fear memories are notoriously difficult to erase, often recovering over time. The longstanding explanation for this finding is that, in extinction training, a new memory is formed that competes with the old one for expression but does not otherwise modify it. This explanation is at odds with traditional models of learning such as Rescorla-Wagner and reinforcement learning. A possible reconciliation that was recently suggested is that extinction training leads to the inference of a new state that is different from the state that was in effect in the original training. This solution, however, raises a new question: under what conditions are new states, or new memories formed? Theoretical accounts implicate persistent large prediction errors in this process. As a test of this idea, we reasoned that careful design of the reinforcement schedule during extinction training could reduce these prediction errors enough to prevent the formation of a new memory, while still decreasing reinforcement sufficiently to drive modification of the old fear memory. In two Pavlovian fear-conditioning experiments, we show that gradually reducing the frequency of aversive stimuli, rather than eliminating them abruptly, prevents the recovery of fear. This finding has important implications for theories of state discovery in reinforcement learning.

  1. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction.

    Science.gov (United States)

    Finnegan, Seth; Rasmussen, Christian M Ø; Harper, David A T

    2016-04-27

    The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician-Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 35°) palaeolatitudinal ranges. This pattern is only observed in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions between shifting climate zones and palaeobiogeography may also have been important. We test the latter hypothesis by estimating whether each genus would have been able to track habitats within its thermal tolerance range during the greenhouse-icehouse climate transition. Models including these estimates are favoured over alternative models. We argue that the LOME, long regarded as non-selective, is highly selective along biogeographic and bathymetric axes that are not closely correlated with taxonomic identity. PMID:27122567

  2. Post-retrieval extinction in adolescence prevents return of juvenile fear.

    Science.gov (United States)

    Jones, Carolyn E; Monfils, Marie-H

    2016-10-01

    Traumatic experiences early in life can contribute to the development of mood and anxiety disorders that manifest during adolescence and young adulthood. In young rats exposed to acute fear or stress, alterations in neural development can lead to enduring behavioral abnormalities. Here, we used a modified extinction intervention (retrieval+extinction) during late adolescence (post-natal day 45 [p45]), in rats, to target auditory Pavlovian fear associations acquired as juveniles (p17 and p25). The effects of adolescent intervention were examined by assessing freezing as adults during both fear reacquisition and social transmission of fear from a cagemate. Rats underwent testing or training at three time points across development: juvenile (p17 or p25), adolescent (p45), and adult (p100). Retrieval+extinction during late adolescence prevented social reinstatement and recovery over time of fears initially acquired as juveniles (p17 and p25, respectively). Adolescence was the only time point tested here where retrieval+extinction prevented fear recall of associations acquired 20+ days earlier. PMID:27634147

  3. Global distribution and drivers of language extinction risk

    DEFF Research Database (Denmark)

    Amano, Tatsuya; Sandel, Brody; Eager, Heidi;

    2014-01-01

    Many of the world's languages face serious risk of extinction. Efforts to prevent this cultural loss are severely constrained by a poor understanding of the geographical patterns and drivers of extinction risk. We quantify the global distribution of language extinction risk-represented by small...

  4. Inhibition of Estradiol Synthesis Impairs Fear Extinction in Male Rats

    Science.gov (United States)

    Graham, Bronwyn M.; Milad, Mohammed R.

    2014-01-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole,…

  5. Age differences in fear retention and extinction in male Sprague-Dawley rats: effects of ethanol challenge during conditioning.

    Science.gov (United States)

    Broadwater, Margaret; Spear, Linda P

    2013-09-01

    Pavlovian fear conditioning is an ideal model to investigate how learning and memory are influenced by alcohol use during adolescence because the neural mechanisms involved have been studied extensively. In Exp 1, adolescent and adult male Sprague-Dawley rats were non-injected or injected with saline, 1 or 1.5 g/kg ethanol intraperitoneally 10 min prior to tone or context conditioning. Twenty-four hours later, animals were tested for tone or context retention and extinction, with examination of extinction retention conducted 24h thereafter. In Exp 2, a context extinction session was inserted between the tone conditioning and the tone fear retention/extinction days to reduce pre-CS baseline freezing levels at test. Basal levels of acquisition, fear retention, extinction, and extinction retention after tone conditioning were similar between adolescent and adult rats. In contrast adolescents showed faster context extinction than adults, while again not differing from adults during context acquisition, retention or extinction retention. In terms of ethanol effects, adolescents were less sensitive to ethanol-induced context retention deficits than adults. No age differences emerged in terms of tone fear retention, with ethanol disrupting tone fear retention at both ages in Exp 1, but at neither age in Exp 2, a difference seemingly due to group differences in pre-CS freezing during tone testing in Exp 1, but not Exp 2. These results suggest that age differences in the acute effects of ethanol on cognitive function are task-specific, and provide further evidence for age differences cognitive functioning in a task thought to be hippocampally related.

  6. Altered ERK1/2 Signaling in the Brain of Learned Helpless Rats: Relevance in Vulnerability to Developing Stress-Induced Depression

    Directory of Open Access Journals (Sweden)

    Yogesh Dwivedi

    2016-01-01

    Full Text Available Extracellular signal-regulated kinase 1/2- (ERK1/2- mediated cellular signaling plays a major role in synaptic and structural plasticity. Although ERK1/2 signaling has been shown to be involved in stress and depression, whether vulnerability to develop depression is associated with abnormalities in ERK1/2 signaling is not clearly known. The present study examined ERK1/2 signaling in frontal cortex and hippocampus of rats that showed vulnerability (learned helplessness, (LH or resiliency (non-learned helplessness, (non-LH to developing stress-induced depression. In frontal cortex and hippocampus of LH rats, we found that mRNA and protein expressions of ERK1 and ERK2 were significantly reduced, which was associated with their reduced activation and phosphorylation in cytosolic and nuclear fractions, where ERK1 and ERK2 target their substrates. In addition, ERK1/2-mediated catalytic activities and phosphorylation of downstream substrates RSK1 (cytosolic and nuclear and MSK1 (nuclear were also lower in the frontal cortex and hippocampus of LH rats without any change in their mRNA or protein expression. None of these changes were evident in non-LH rats. Our study indicates that ERK1/2 signaling is differentially regulated in LH and non-LH rats and suggests that abnormalities in ERK1/2 signaling may be crucial in the vulnerability to developing depression.

  7. From Pavlov to PTSD: The extinction of conditioned fear in rodents, humans, and in anxiety disorders

    Science.gov (United States)

    VanElzakker, Michael B.; Dahlgren, M. Kathryn; Davis, F. Caroline; Dubois, Stacey; Shin, Lisa M.

    2014-01-01

    Nearly 100 years ago, Ivan Pavlov demonstrated that dogs could learn to use a neutral cue to predict a biologically relevant event: after repeated predictive pairings, Pavlov's dogs were conditioned to anticipate food at the sound of a bell, which caused them to salivate. Like sustenance, danger is biologically relevant, and neutral cues can take on great salience when they predict a threat to survival. In anxiety disorders such as posttraumatic stress disorder (PTSD), this type of conditioned fear fails to extinguish, and reminders of traumatic events can cause pathological conditioned fear responses for decades after danger has passed. In this review, we use fear conditioning and extinction studies to draw a direct line from Pavlov to PTSD and other anxiety disorders. We explain how rodent studies have informed neuroimaging studies of healthy humans and humans with PTSD. We describe several genes that have been linked to both PTSD and fear conditioning and extinction and explain how abnormalities in fear conditioning or extinction may reflect a general biomarker of anxiety disorders. Finally, we explore drug and neuromodulation treatments that may enhance therapeutic extinction in anxiety disorders. PMID:24321650

  8. The role of the medial prefrontal cortex in the conditioning and extinction of fear

    Directory of Open Access Journals (Sweden)

    Thomas Francis Giustino

    2015-11-01

    Full Text Available Once acquired, a fearful memory can persist for a lifetime. Although learned fear can be extinguished, extinction memories are fragile. The resilience of fear memories to extinction may contribute to the maintenance of disorders of fear and anxiety, including post-traumatic stress disorder (PTSD. As such, considerable effort has been placed on understanding the neural circuitry underlying the acquisition, expression, and extinction of emotional memories in rodent models as well as in humans. A triad of brain regions, including the prefrontal cortex, hippocampus, and amygdala, form an essential brain circuit involved in fear conditioning and extinction. Within this circuit, the prefrontal cortex is thought to exert top-down control over subcortical structures to regulate appropriate behavioral responses. Importantly, a division of labor has been proposed in which the prelimbic (PL and infralimbic (IL subdivisions of the medial prefrontal cortex (mPFC regulate the expression and suppression of fear in rodents, respectively. Here we critically review the anatomical and physiological evidence that has led to this proposed dichotomy of function within mPFC. We propose that under some conditions, the PL and IL act in concert, exhibiting similar patterns of neural activity in response to aversive conditioned stimuli and during the expression or inhibition of conditioned fear. This may stem from common synaptic inputs, parallel downstream outputs, or cortico-cortical interactions. Despite this functional covariation, these mPFC subdivisions may still be coding for largely opposing behavioral outcomes, with PL biased towards fear expression and IL towards suppression.

  9. Mass Extinction in a Simple Mathematical Biological Model

    CERN Document Server

    Tokita, K; Tokita, Kei; Yasutomi, Ayumu

    1997-01-01

    Introducing the effect of extinction into the so-called replicator equations in mathematical biology, we construct a general model of ecosystems. The present model shows mass extinction by its own extinction dynamics when the system initially has a large number of species ( diversity). The extinction dynamics shows several significant features such as a power law in basin size distribution, induction time, etc. The present theory can be a mathematical foundation of the species-area effect in the paleontologic theory for mass extinction.

  10. Decline and local extinction of Fucales in French Riviera: the harbinger of future extinctions?

    Directory of Open Access Journals (Sweden)

    T. THIBAUT

    2015-01-01

    Full Text Available The French Riviera is one of the Mediterranean areas that has been longest and most thoroughly impacted by human activities. Fucales are long-lived, large-sized brown algae that constitute a good model for studying human impact on species diversity. We gathered all historical data (literature and herbarium vouchers, since the early 19th century, to reconstruct their distribution. The current distribution was established from a 7-year (2007-2013 survey of the 212-km shoreline (1/2 500 map, by means of boating, snorkelling and scuba diving. Overall, 18 taxa of Cystoseira and Sargassum have been reported. Upon comparison with historical data, 5 taxa were no longer observed (C. elegans, C. foeniculacea f. latiramosa, C. squarrosa, C. spinosa var. spinosa and S. hornschuchii while C. jabukae, previously unrecorded, was observed. In addition to these  taxa, probably extinct at a local scale, some taxa had suffered a dramatic decline (C. barbata f. barbata, C. crinita, C. spinosa var. compressa and S. acinarium or become nearly extinct (C. foeniculacea f. tenuiramosa. Three of them, which played in the past significant functional roles in coastal communities, can be considered as functionally extinct. Possible causes of decline and local extinction are discussed. A similar situation has already been reported, although at a much more local scale, in a variety of Mediterranean localities. The question therefore arises about the status of Fucales species in the Mediterranean: are some species on the brink of extinction? Is their extinction at the scale of the French Riviera the harbinger of their extinction Mediterranean–wide?

  11. Large Scale Extinction Maps with UVIT

    CERN Document Server

    Ravichandran, S; Safonova, Margarita; Murthy, Jayant

    2013-01-01

    The Ultraviolet Imaging Telescope (UVIT) is scheduled to be launched as a part of the ASTROSAT satellite. As part of the mission planning for the instrument we have studied the efficacy of UVIT observations for interstellar extinction measurements. We find that in the best case scenario, the UVIT can measure the reddening to an accuracy of about 0.02 magnitudes, which combined with the derived distances to the stars, will enable us to model the three-dimensional distribution of extinction in our Galaxy. The knowledge of the distribution of the ISM will then be used to study distant objects, affected by it. This work points the way to further refining the UVIT mission plan to best satisfy different science studies.

  12. How Colored Environmental Noise Affects Population Extinction

    Science.gov (United States)

    Kamenev, Alex; Meerson, Baruch; Shklovskii, Boris

    2008-12-01

    Environmental noise can cause an exponential reduction in the mean time to extinction (MTE) of an isolated population. We study this effect on an example of a stochastic birth-death process with rates modulated by a colored (that is, correlated) Gaussian noise. A path integral formulation yields a transparent way of evaluating the MTE and finding the optimal realization of the environmental noise that determines the most probable path to extinction. The population-size dependence of the MTE changes from exponential in the absence of the environmental noise to a power law for a short-correlated noise and to no dependence for long-correlated noise. We also establish the validity domains of the white-noise limit and adiabatic limit.

  13. Transmittance Fluctuation from Nearly Extinct Nematic Cells

    Science.gov (United States)

    Sumiyoshi, Ken

    2010-04-01

    By introducing geometrical optics approximation (GOA) solutions to a nearly extinct homogeneous nematic director, the effects of assembly misalignment and director fluctuation on light leakage transmittance are studied. Transmittance expressions including fluctuation swing are obtained for three misoriented cases: misaligned homogeneous case, misaligned analyzer case, and mistwisted nematic case. Except for the misaligned homogeneous case with second-order fluctuation, all the other expressions have a linear contribution caused by their own misorientation. From these results, the transmittance variance from fluctuation at a misaligned situation is more enhanced than that in the extinction situation. After introducing thermal average statistics, expressions for the average and variance of transmittance with fluctuation are given. A numerical estimation for these expressions shows that in the misaligned homogeneous case by 1°, the standard deviation of transmittance is 20% of its average.

  14. Population extinction and the genetics of adaptation.

    Science.gov (United States)

    Orr, H Allen; Unckless, Robert L

    2008-08-01

    Theories of adaptation typically ignore the effect of environmental change on population size. But some environmental challenges--challenges to which populations must adapt--may depress absolute fitness below 1, causing populations to decline. Under this scenario, adaptation is a race; beneficial alleles that adapt a population to the new environment must sweep to high frequency before the population becomes extinct. We derive simple, though approximate, solutions to the probability of successful adaptation (population survival) when adaptation involves new mutations, the standing genetic variation, or a mixture of the two. Our results show that adaptation to such environmental challenges can be difficult when relying on new mutations at one or a few loci, and populations will often decline to extinction. PMID:18662122

  15. Visuomotor links in awareness: evidence from extinction.

    Science.gov (United States)

    Ricci, Raffaella; Genero, Rosanna; Colombatti, Simona; Zampieri, Daniela; Chatterjee, Anjan

    2005-05-31

    In patients with extinction, ipsilesional stimuli may abolish awareness of contralesional stimuli. Explanations of extinction often assume a serial model of processing in which sensory competition and identification precedes the selection of responses. We tested the adequacy of this assumption by examining the effects of response variables on visual awareness in six patients using signal detection analysis. Ipsilesional stimuli modulated patients' response criteria in deciding whether a contralesional stimulus was a target, and response modality (verbal or motor) modulated patients' abilities to discriminate between contralesional targets and distractors. This pattern of input variables modulating response criteria and output variables modulating discriminability indicates the extent to which attentional and intentional systems are tightly intertwined, with bi-directional effects in producing visual awareness.

  16. Extinction of corrugated hydrogen/air flames

    International Nuclear Information System (INIS)

    Recent studies on flammability limits reveal the importance of flow nonuniformity, flame curvature, and molecular and thermal diffusivities in determining the extinguishability and the associated limits of premixed fuel/air flames. In particular, it is found that conditions which favor extinction of a lean flame may cause intensification of a rich flame. In the present study the authors have experimentally determined the extinction characteristics and limits of highly curved hydrogen/air flames as represented by the opening of bunsen flame tips. Results show that the tip opens at a constant fuel equivalence ratio of phi = 1.15, regardless of the velocity and uniformity of the upstream flow. This critical mixture concentration, while being rich, is still on the lean side of that corresponding to the maximum burning velocity (phi = 1.8), implying that for highly diffusive systems, the relevant reference concentration is that for maximum burning velocity instead of stoichiometry

  17. Causes and timing of future biosphere extinction

    Science.gov (United States)

    Franck, S.; Bounama, C.; von Bloh, W.

    2005-11-01

    We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the aggregated reservoir ocean and atmosphere. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. We find that from the Archaean to the future a procaryotic biosphere always exists. 2 Gyr ago eucaryotic life first appears. The emergence of complex multicellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We show that there is no evidence for an implosion-like extinction in contrast to the Cambrian explosion. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.

  18. Simple models of evolution and extinction

    CERN Document Server

    Newman, M E J

    1999-01-01

    This article gives a brief introduction to the mathematical modeling of large-scale biological evolution and extinction. We give three examples of simple models in this field: the coevolutionary avalanche model of Bak and Sneppen, the environmental stress model of Newman, and the increasing fitness model of Sibani, Schmidt, and Alstrom. We describe the features of real evolution which these models are intended to explain and compare the results of simulations against data drawn from the fossil record.

  19. Simple models of evolution and extinction

    OpenAIRE

    Newman, M. E. J.

    1999-01-01

    This article gives a brief introduction to the mathematical modeling of large-scale biological evolution and extinction. We give three examples of simple models in this field: the coevolutionary avalanche model of Bak and Sneppen, the environmental stress model of Newman, and the increasing fitness model of Sibani, Schmidt, and Alstrom. We describe the features of real evolution which these models are intended to explain and compare the results of simulations against data drawn from the fossi...

  20. Effects of broken affordance on visual extinction.

    Science.gov (United States)

    Wulff, Melanie; Humphreys, Glyn W

    2015-01-01

    Previous studies have shown that visual extinction can be reduced if two objects are positioned to "afford" an action. Here we tested if this affordance effect was disrupted by "breaking" the affordance, i.e., if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006), extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool) and unrelated tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  1. Effects of broken affordance on visual extinction

    Directory of Open Access Journals (Sweden)

    Melanie eWulff

    2015-09-01

    Full Text Available Previous studies have shown that visual extinction can be reduced if two objects are positioned to afford an action. Here we tested if this affordance effect was disrupted by breaking the affordance – if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006, extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool and unrelated tool-tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  2. Opportunities and costs for preventing vertebrate extinctions.

    Science.gov (United States)

    Conde, Dalia A; Colchero, Fernando; Güneralp, Burak; Gusset, Markus; Skolnik, Ben; Parr, Michael; Byers, Onnie; Johnson, Kevin; Young, Glyn; Flesness, Nate; Possingham, Hugh; Fa, John E

    2015-03-16

    Despite an increase in policy and management responses to the global biodiversity crisis, implementation of the 20 Aichi Biodiversity Targets still shows insufficient progress [1]. These targets, strategic goals defined by the United Nations Convention on Biological Diversity (CBD), address major causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2], a consortium of conservation-oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 'trigger' sites [3]. These are arguably the most irreplaceable category of important biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1]. Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species [2]. However, averting human-induced species extinctions within AZE sites requires enhanced planning tools to increase the chances of success [3]. Here, we assess the potential for ensuring the long-term conservation of AZE vertebrate species (157 mammals, 165 birds, 17 reptiles and 502 amphibians) by calculating a conservation opportunity index (COI) for each species. The COI encompasses a set of measurable indicators that quantify the possibility of achieving successful conservation of a species in its natural habitat (COIh) and by establishing insurance populations in zoos (COIc).

  3. Geography of cretaceous extinctions: Data base development

    Science.gov (United States)

    Raup, D. M.

    1991-01-01

    Data bases built from the source literature are plagued by problems of data quality. Unless the data acquisition is done by experts, working slowly, the data base may contain so much garbage that true signals and patterns cannot be detected. On the other hand, high quality data bases develop so slowly that satisfactory statistical analysis may never be possible due to the small sample sizes. Results of a test are presented of the opposite strategy: rapid data acquisition by non-experts with minimal control on data quality. A published list of 186 species and genera of fossil invertibrates of the latest Cretaceous Age (Maestrichtian) were located through a random search of the paleobiological and geological literature. The geographic location for each faunal list was then transformed electronically to Maestrichtian latitude and longitude and the lists were further digested to identify the genera occurring in each ten-degree, latitude-longitude block. The geographical lists were clustered using the Otsuka similarity coefficient and a standard unweight-pair-group method. The resulting clusters are remarkably consistent geographically, indicating that a strong biogeographic signal is visible despite low-quality data. A further test evaluated the geographic pattern of end-Cretaceaous extinctions. All genera in the data base were compared with Sepkoski's compendium of time ranges of genera to determine which of the reported genera survived the Cretaceous mass extinction. In turn, extinction rates for the ten-degree, latitude-longitude blocks were mapped. The resulting distribution is readily interpretable as a robust pattern of the geography of the mass extinction. The study demonstrates that a low-quality data base, built rapidly, can provide a basis for meaningful analysis of past biotic events.

  4. Dynamics of extinction debt across five taxonomic groups.

    Science.gov (United States)

    Halley, John M; Monokrousos, Nikolaos; Mazaris, Antonios D; Newmark, William D; Vokou, Despoina

    2016-01-01

    Species extinction following habitat loss is well documented. However, these extinctions do not happen immediately. The biodiversity surplus (extinction debt) declines with some delay through the process of relaxation. Estimating the time constants of relaxation, mainly the expected time to first extinction and the commonly used time for half the extinction debt to be paid off (half-life), is crucial for conservation purposes. Currently, there is no agreement on the rate of relaxation and the factors that it depends on. Here we find that half-life increases with area for all groups examined in a large meta-analysis of extinction data. A common pattern emerges if we use average number of individuals per species before habitat loss as an area index: for mammals, birds, reptiles and plants, the relationship has an exponent close to a half. We also find that the time to first determined extinction is short and increases slowly with area. PMID:27452815

  5. Large-body impact and extinction in the Phanerozoic

    Science.gov (United States)

    Raup, D. M.

    1992-01-01

    The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts are responsible for all "pulsed" extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.

  6. Extinction and dust properties in a clumpy medium

    CERN Document Server

    Scicluna, P

    2015-01-01

    (abridged) The dust content of the universe is primarily explored via its interaction with stellar photons, producing interstellar extinction. However, owing to the physical extension of the observing beam, observations may detect scattered photons, resulting in a change in the observed (or effective) extinction, depending on the spatial distribution of the dust and the resolution of the instrument. We investigate the influence of clumpy dust distributions on effective extinction toward embedded sources and those in the diffuse ISM. We use Monte Carlo radiative transfer to examine effective extinction for various geometries. By varying the number, optical depth and volume-filling factor of clumps in models of spherical shells and the diffuse ISM, we explore the evolution of extinction. Depending on the number of scattering events in the beam, the extinction curve steepens in homogeneous media and flattens in clumpy media. As a result, clumpy dust distributions can to reproduce extinction curves with arbitrary...

  7. Glucocorticoids enhance extinction-based psychotherapy.

    Science.gov (United States)

    de Quervain, Dominique J-F; Bentz, Dorothée; Michael, Tanja; Bolt, Olivia C; Wiederhold, Brenda K; Margraf, Jürgen; Wilhelm, Frank H

    2011-04-19

    Behavioral exposure therapy of anxiety disorders is believed to rely on fear extinction. Because preclinical studies have shown that glucocorticoids can promote extinction processes, we aimed at investigating whether the administration of these hormones might be useful in enhancing exposure therapy. In a randomized, double-blind, placebo-controlled study, 40 patients with specific phobia for heights were treated with three sessions of exposure therapy using virtual reality exposure to heights. Cortisol (20 mg) or placebo was administered orally 1 h before each of the treatment sessions. Subjects returned for a posttreatment assessment 3-5 d after the last treatment session and for a follow-up assessment after 1 mo. Adding cortisol to exposure therapy resulted in a significantly greater reduction in fear of heights as measured with the acrophobia questionnaire (AQ) both at posttreatment and at follow-up, compared with placebo. Furthermore, subjects receiving cortisol showed a significantly greater reduction in acute anxiety during virtual exposure to a phobic situation at posttreatment and a significantly smaller exposure-induced increase in skin conductance level at follow-up. The present findings indicate that the administration of cortisol can enhance extinction-based psychotherapy.

  8. Modelling dust extinction in the Magellanic Clouds

    CERN Document Server

    Zonca, Alberto; Mulas, Giacomo; Aresu, Giambattista; Cecchi-Pestellini, Cesare

    2015-01-01

    We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting by core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons. All different flavors of the extinction curves observed in the Magellanic Clouds can be described by the present model, that has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the Magellanic Clouds the extinction produced by classic grains is generally larger than absorption by polycyclic aromatic hydrocarbons. Within this model, the non-linear far-UV rise is accounted for by polycyclic aromatic hydrocarbons, whose presence in turn is always associated to a gap in the size distribution of classical particles. This hints either a physical connection between (e.g., a common cause for) polycyclic aromatic hydrocarbons and the absence of middle-sized dust particles, or the need for an additional component...

  9. Rewinding the process of mammalian extinction.

    Science.gov (United States)

    Saragusty, Joseph; Diecke, Sebastian; Drukker, Micha; Durrant, Barbara; Friedrich Ben-Nun, Inbar; Galli, Cesare; Göritz, Frank; Hayashi, Katsuhiko; Hermes, Robert; Holtze, Susanne; Johnson, Stacey; Lazzari, Giovanna; Loi, Pasqualino; Loring, Jeanne F; Okita, Keisuke; Renfree, Marilyn B; Seet, Steven; Voracek, Thomas; Stejskal, Jan; Ryder, Oliver A; Hildebrandt, Thomas B

    2016-07-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280-292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

  10. Mathematical Modeling of Extinction of Inhomogeneous Populations.

    Science.gov (United States)

    Karev, G P; Kareva, I

    2016-04-01

    Mathematical models of population extinction have a variety of applications in such areas as ecology, paleontology and conservation biology. Here we propose and investigate two types of sub-exponential models of population extinction. Unlike the more traditional exponential models, the life duration of sub-exponential models is finite. In the first model, the population is assumed to be composed of clones that are independent from each other. In the second model, we assume that the size of the population as a whole decreases according to the sub-exponential equation. We then investigate the "unobserved heterogeneity," i.e., the underlying inhomogeneous population model, and calculate the distribution of frequencies of clones for both models. We show that the dynamics of frequencies in the first model is governed by the principle of minimum of Tsallis information loss. In the second model, the notion of "internal population time" is proposed; with respect to the internal time, the dynamics of frequencies is governed by the principle of minimum of Shannon information loss. The results of this analysis show that the principle of minimum of information loss is the underlying law for the evolution of a broad class of models of population extinction. Finally, we propose a possible application of this modeling framework to mechanisms underlying time perception. PMID:27090117

  11. Environmental variation, stochastic extinction, and competitive coexistence.

    Science.gov (United States)

    Adler, Peter B; Drake, John M

    2008-11-01

    Understanding how environmental fluctuations affect population persistence is essential for predicting the ecological impacts of expected future increases in climate variability. However, two bodies of theory make opposite predictions about the effect of environmental variation on persistence. Single-species theory, common in conservation biology and population viability analyses, suggests that environmental variation increases the risk of stochastic extinction. By contrast, coexistence theory has shown that environmental variation can buffer inferior competitors against competitive exclusion through a storage effect. We reconcile these two perspectives by showing that in the presence of demographic stochasticity, environmental variation can increase the chance of extinction while simultaneously stabilizing coexistence. Our stochastic simulations of a two-species storage effect model reveal a unimodal relationship between environmental variation and coexistence time, implying maximum coexistence at intermediate levels of environmental variation. The unimodal pattern reflects the fact that the stabilizing influence of the storage effect accumulates rapidly at low levels of environmental variation, whereas the risk of extinction due to the combined effects of environmental variation and demographic stochasticity increases most rapidly at higher levels of variation. Future increases in environmental variation could either increase or decrease an inferior competitor's expected persistence time, depending on the distance between the present level of environmental variation and the optimal level anticipated by this theory. PMID:18817458

  12. Causes and timing of future biosphere extinctions

    Directory of Open Access Journals (Sweden)

    S. Franck

    2006-01-01

    Full Text Available We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the combined ocean and atmosphere reservoir. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. During the entire existence of the biosphere procaryotes are always present. 2 Gyr ago eucaryotic life first appears. The emergence of complex multicellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We show that there is no evidence for an implosion-like extinction in contrast to the Cambrian explosion. In dependence of their temperature tolerance complex multicellular life and eucaryotes become extinct in about 0.8–1.2 Gyr and 1.3–1.5 Gyr, respectively. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.

  13. Causes and timing of future biosphere extinctions

    Science.gov (United States)

    Franck, S.; Bounama, C.; von Bloh, W.

    2006-03-01

    We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the combined ocean and atmosphere reservoir. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. During the entire existence of the biosphere procaryotes are always present. 2 Gyr ago eucaryotic life first appears. The emergence of complex multicellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We show that there is no evidence for an implosion-like extinction in contrast to the Cambrian explosion. In dependence of their temperature tolerance complex multicellular life and eucaryotes become extinct in about 0.8-1.2 Gyr and 1.3-1.5 Gyr, respectively. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.

  14. Minimizing extinction risk through genetic rescue

    Directory of Open Access Journals (Sweden)

    Waite, T. A.

    2005-12-01

    Full Text Available According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus. We ask how many migrants per generation (MPG are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations. During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10. Compared with the 0-MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi-extinction suggests that replicate populations in the 1-MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue.

  15. Intake of High-intensity Sweeteners alters the Ability of Sweet Taste to Signal Caloric Consequences: Implications for the Learned Control of Energy and Body Weight Regulation

    Science.gov (United States)

    Davidson, Terry L.; Martin, Ashley A.; Clark, Kiely; Swithers, Susan E.

    2012-01-01

    Recent results from both human epidemiological and experimental studies with animals suggest that intake of non-caloric sweeteners may promote, rather than protect against, weight gain and other disturbances of energy regulation. However, without a viable mechanism to explain how consumption of non-caloric sweeteners can increase energy intake and body weight, the persuasiveness of such results has been limited. Using a rat model, the present research showed that intake of non-caloric sweeteners reduces the effectiveness of learned associations between sweet tastes and postingestive caloric outcomes (Experiment 1) and that interfering with this association may impair the ability of rats to regulate their intake of sweet, but not nonsweet, high-fat and high-calorie food (Experiment 2). The results support the hypothesis that consuming noncaloric sweeteners may promote excessive intake and body weight gain by weakening a predictive relationship between sweet taste and the caloric consequences of eating. PMID:21424985

  16. The Younger Dryas ET Impact Theory and Terminal Pleistocene Mammalian Extinctions in North America

    Science.gov (United States)

    Erlandson, J. M.; Kennett, D. J.; Kennett, J.; Braje, T.; Culleton, B.

    2007-05-01

    Despite decades of intensive study and debate, no consensus has been reached on what caused the extinction of North America's mammalian megafauna at the end of the Pleistocene. In a scholarly standoff, prominent scientists have shown that neither "human overkill" or "climate change" models adequately account for the patterns found in the paleontological and archaeological records of North America. The Younger Dryas ET Impact theory may dramatically alter this debate, adding a catastrophic trigger to help explain the rapid extinction of many large mammals about 12,900 years ago. New data suggest that an extraterrestrial impact focused in northern and eastern North America may have devastated the megafauna through: (1) direct mortality caused by the impacts shock wave, debris, and massive wildfires; (2) dramatic reduction of terrestrial food supplies, rapid climatic change, and ecological reorganization; and (3) coup-de-grace effects of surviving human populations rapidly expanding after the impact.

  17. Effects of substitution on counterflow ignition and extinction of C3 and C4 alcohols

    KAUST Repository

    Alfazazi, Adamu

    2016-06-17

    Dwindling reserves and inherent uncertainty in the price of conventional fuels necessitates a search for alternative fuels. Alcohols represent a potential source of energy for the future. The structural features of an alcohol fuel have a direct impact on combustion properties. In particular, substitution in alcohols can alter the global combustion reactivity. In this study, experiments and numerical simulations were conducted to investigate the critical conditions of extinction and autoignition of n-propanol, 1-butanol, iso-propanol and iso-butanol in non-premixed diffusion flames. Experiments were carried out in the counterflow configuration, while simulations were conducted using a skeletal chemical kinetic model for the C3 and C4 alcohols. The fuel stream consists of the pre-vaporized fuel diluted with nitrogen, while the oxidizer stream is air. The experimental results show that autoignition temperatures of the tested alcohols increase in the following order: iso-propanol > iso-butanol > 1-butanol ≈ n-propanol. The simulated results for the branched alcohols agree with the experiments, while the autoignition temperature of 1-butanol is slightly higher than that of n-propanol. For extinction, the experiments show that the extinction limits of the tested fuels increase in the following order: n-propanol ≈ 1-butanol > iso-butanol > iso-propanol. The model suggests that the extinction limits of 1-butanol is slightly higher than n-propanol with extinction strain rate of iso-butanol and iso-propanol maintaining the experimentally observed trend. The transport weighted enthalpy (TWE) and radical index (Ri) concepts were utilized to rationalize the observed reactivity trends for these fuels.

  18. Past, present and future of host–parasite co-extinctions

    Directory of Open Access Journals (Sweden)

    Giovanni Strona

    2015-12-01

    Full Text Available Human induced ecosystem alterations and climate change are expected to drive several species to extinction. In this context, the attention of public opinion, and hence conservationists' efforts, are often targeted towards species having emotional, recreational and/or economical value. This tendency may result in a high number of extinctions happening unnoticed. Among these, many could involve parasites. Several studies have highlighted various reasons why we should care about this, that go far beyond the fact that parasites are amazingly diverse. A growing corpus of evidence suggests that parasites contribute much to ecosystems both in terms of biomass and services, and the seemingly paradoxical idea that a healthy ecosystem is one rich in parasites is becoming key to the whole concept of parasite conservation. Although various articles have covered different aspects of host–parasite co-extinctions, I feel that some important conceptual issues still need to be formally addressed. In this review, I will attempt at clarifying some of them, with the aim of providing researchers with a unifying conceptual framework that could help them designing future studies. In doing this, I will try to draw a more clear distinction between the (co-evolutionary and the ecological dimensions of co-extinction studies, since the ongoing processes that are putting parasites at risk now operate at a scale that is extremely different from the one that has shaped host–parasite networks throughout million years of co-evolution. Moreover, I will emphasize how the complexity of direct and indirect effects of parasites on ecosystems makes it much challenging to identify the mechanisms possibly leading to co-extinction events, and to predict how such events will affect ecosystems in the long run.

  19. Warming-induced changes in predation, extinction and invasion in an ectotherm food web.

    Science.gov (United States)

    Seifert, Linda I; Weithoff, Guntram; Gaedke, Ursula; Vos, Matthijs

    2015-06-01

    Climate change will alter the forces of predation and competition in temperate ectotherm food webs. This may increase local extinction rates, change the fate of invasions and impede species reintroductions into communities. Invasion success could be modulated by traits (e.g., defenses) and adaptations to climate. We studied how different temperatures affect the time until extinction of species, using bitrophic and tritrophic planktonic food webs to evaluate the relative importance of predatory overexploitation and competitive exclusion, at 15 and 25 °C. In addition, we tested how inclusion of a subtropical as opposed to a temperate strain in this model food web affects times until extinction. Further, we studied the invasion success of the temperate rotifer Brachionus calyciflorus into the planktonic food web at 15 and 25 °C on five consecutive introduction dates, during which the relative forces of predation and competition differed. A higher temperature dramatically shortened times until extinction of all herbivore species due to carnivorous overexploitation in tritrophic systems. Surprisingly, warming did not increase rates of competitive exclusion among the tested herbivore species in bitrophic communities. Including a subtropical herbivore strain reduced top-down control by the carnivore at high temperature. Invasion attempts of temperate B. calyciflorus into the food web always succeeded at 15 °C, but consistently failed at 25 °C due to voracious overexploitation by the carnivore. Pre-induction of defenses (spines) in B. calyciflorus before the invasion attempt did not change its invasion success at the high temperature. We conclude that high temperatures may promote local extinctions in temperate ectotherms and reduce their chances of successful recovery. PMID:25564019

  20. The path to host extinction can lead to loss of generalist parasites.

    Science.gov (United States)

    Farrell, Maxwell J; Stephens, Patrick R; Berrang-Ford, Lea; Gittleman, John L; Davies, T Jonathan

    2015-07-01

    Host extinction can alter disease transmission dynamics, influence parasite extinction and ultimately change the nature of host-parasite systems. While theory predicts that single-host parasites are among the parasite species most susceptible to extinction following declines in their hosts, documented parasite extinctions are rare. Using a comparative approach, we investigate how the richness of single-host and multi-host parasites is influenced by extinction risk among ungulate and carnivore hosts. Host-parasite associations for free-living carnivores (order Carnivora) and terrestrial ungulates (orders Perissodactyla + Cetartiodactyla minus cetaceans) were merged with host trait data and IUCN Red List status to explore the distribution of single-host and multi-host parasites among threatened and non-threatened hosts. We find that threatened ungulates harbour a higher proportion of single-host parasites compared to non-threatened ungulates, which is explained by decreases in the richness of multi-host parasites. However, among carnivores threat status is not a significant predictor of the proportion of single-host parasites, or the richness of single-host or multi-host parasites. The loss of multi-host parasites from threatened ungulates may be explained by decreased cross-species contact as hosts decline and habitats become fragmented. Among carnivores, threat status may not be important in predicting patterns of parasite specificity because host decline results in equal losses of both single-host parasites and multi-host parasites through reduction in average population density and frequency of cross-species contact. Our results contrast with current models of parasite coextinction and highlight the need for updated theories that are applicable across host groups and account for both inter- and intraspecific contact.